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DAVID J. MALAN: All right.

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This is CS50's Introduction
to Cybersecurity.

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My name is David Malan.

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And this week, let's focus
on preserving privacy.

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Indeed, over the past
several weeks, we've

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focused on securing your accounts,
your data, your systems, your software.

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And all of that is really about keeping
communications between points A and B,

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for instance, secure, so
that no one in between

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can actually access the
information you're trying to share.

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But what if you, A, don't even want
B to have some of that information?

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So indeed, today, let's focus
on some of the technologies

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that you and I use every day
and some of the technologies

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that underlie the
software, and applications,

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and more that you and I are
going to use tomorrow and beyond

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and consider exactly what
information we're sharing now,

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perhaps, even without
our knowledge and also

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empower you with certain mechanisms
via which you can perhaps

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restrict all the more
of this information

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if you, indeed, do not want
to share it beyond yourself.

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So let's consider first
some of the obvious features

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that you and I probably use every
day, like your web browsing history.

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Whether you're on a laptop,
or desktop, or mobile device,

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odds are you know by now
that your browser tends

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to keep track of pretty much everywhere
you go on the World Wide Web.

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That is to say, if you
click on your URL bar,

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you can sometimes browse through
the past few URLs that you visited.

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If you go up to your browser's
history via some menu,

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you can probably see
everything you've done

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earlier today, yesterday,
last week, last year,

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or perhaps, even the
entirety of your history,

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particularly, if you're logging
into your Google account,

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Microsoft account, or something else.

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So the web browsing history is sort
of both a concern when it comes

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to your privacy, but also a feature.

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Well, let's first consider the feature.

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Well, why is that useful?

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Well, one, I mean, even
I occasionally go back

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through my history
trying to find some web

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page that I know I was
looking at earlier in the day,

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or yesterday, or some
previous time in the past

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because it just helps me find
information more quickly.

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And so in that sense, it
might solve a problem for me.

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Moreover, you probably have noticed
that your web browsing history is often

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used for features like autocomplete.

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So when you start typing
a URL or maybe even

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a keyword that was in
the name of a page,

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your browser might remember much more
quickly what it is you're looking for.

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So you can just hit Enter or click.

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And voila, you're at that same page.

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But of course, this is a concern,
potentially, for your privacy,

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whereby, you might not want someone else
who has physical access to your device

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to start poking through
where it is you've gone.

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You might not want someone else to
have access if you just so happen

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to visit that website or those
websites on maybe a computer in a lab

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environment, or an
internet cafe, or the like.

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So you can imagine quite
a few scenarios in which

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this is, yes, a feature, but quite a
few other scenarios in which this is not

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really a desirable
feature because it invades

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your privacy in some sense,
or at least, puts it at risk

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for being invaded by someone else.

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So we'll consider how we might
at least sanitize this history

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or remove it altogether in ways
that you might already know about.

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For instance, you're probably
already familiar with some option

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in your browser, whereby, you
can clear your browser history.

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And that forgets,
therefore, all of the places

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that you've been, all of the cookies
that you might have accumulated,

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all of the usernames
and passwords that might

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have been remembered by your browser.

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Although, that tends to be a
fairly heavy-handed solution

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because when you clear your
browser history, assuming you

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check all of those
boxes, all of it is gone.

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And that might mean negatively that
you're now logged out of Google,

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you're now logged out of
Outlook, or some other account

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that you actually
still want to use, even

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if you just wanted to clear your
history from something else altogether.

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So we'll consider then
what else might be

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a concern when it comes to your
privacy beyond your own browser.

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And in fact, it doesn't even matter
if you sanitize your own web browsing

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history and delete the entirety
of it because it turns out

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that typically, any website
you visit is, itself,

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on the server side also keeping track
of a lot of that same information.

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That is to say that servers
typically have logs.

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And these are not only
for diagnostic purposes.

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In case anything goes
wrong, the IT staff

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can use those logs to
reconstruct history

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and figure it out, figure
out who was doing what

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and when and how that
might explain some problem.

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It might be used for
auditing purposes if they

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want to keep track of exactly
what was accessed on a system.

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It might be used for
advertising purposes

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or analytical purposes
more generally to mine

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or analyze that data to figure out how
we might monetize it or do something

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else with that same information.

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But what do we mean
concretely when we say

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that information is logged on a server?

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Well, it's very similar to
your own web browsing history,

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but it's even more detailed.

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So here, for instance, is a
representative piece of configuration

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that captures what is a very
common convention for information

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that servers log, web
servers, specifically,

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when you visit them with a browser.

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And I'll highlight
just a subset thereof.

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This log format, the
so-called combined format,

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indicates to me that it's
very common for a server

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when you visit some web page on it that
the server will log, that is, remember

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your remote address, otherwise
known as your IP address.

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It will remember the day and time
at which you accessed that page.

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It will remember exactly
what you requested,

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so the name of the file
or folder on the server

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specifically that you sought
to download or look at.

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It'll remember the referrer, that
is, the URL from which you came.

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And it will even remember
the user agent that you use,

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that is to say your browser.

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So perhaps, unbeknownst
to you, every time

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you use your browser to
visit some website, inside

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of that virtual envelope is quite
a bit more than just the request

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that you're making of the browser--

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of the server, rather.

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It includes, yes, your IP
address and on the outside

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of the envelope, as we've
described it in the past.

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It includes some number of HTTP
headers, as we've discussed in the past.

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But in particular, it
includes information

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that you might not want being
stored on servers in perpetuity

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and you have no control
over deleting necessarily.

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Unless there is some regulatory
requirement or law that

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requires that the server delete
it for you on some schedule,

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you have much, much less
control over this information.

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So let's consider in a
bit more technical detail

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what some of this
information is and how you

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might at least exert some control
over just how much of that information

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is being shared.

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So let's revisit first this
building block of HTTP headers

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that we keep coming back to if only
because in the world of systems

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and software nowadays, things
on the web are just so common.

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Using HTML, CSS, JavaScript, using
web browsers and web servers,

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that's driving a lot
of today's interactions

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with technology, whether
it's in native applications

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or whether it's with mobile websites,
or desktop websites, or the like.

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So HTTP headers, recall, are
just like key value pairs

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that are inside of those
virtual envelopes that

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indicate some kind of setting or
some kind of piece of information

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that the browser is
sending to the server

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or that the server is
sending to the browser.

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So for instance, if I go
on google.com and I search,

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as I often do, for cats, well, what
might be going on underneath the hood?

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Well, in that web page that Google
gives me with 10, or 20, or 30,

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or six billion, 240 million cats, there
might be HTML that looks like this.

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And recall that this
HTML, which I'm proposing

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exists somewhere in Google search
results, is an anchor tag for a link.

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There's the n tag over there.

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The hyper-reference for
this link, or href attribute

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has a value of
https://example.com, for instance.

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And the word that the human will
see is cats, literally in this case.

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Now, I'm assuming for the
sake of discussion that today,

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example.com is a website full of cats.

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And that's why it might be appearing
among Google search results

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when I search for cats as my keyword.

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But when a user like you or me
clicks on that link on google.com,

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because that is literally where
you're looking at the search

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results in this story, it turns out that
your browser not only goes and requests

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that web page, your browser
includes an HTTP header

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like this in that virtual envelope.

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That's specifically called referrer--
that's the key in this case--

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the value of which is the
URL from which you came.

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So for instance, if I have just gone to
google.com, and I've searched for cats,

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and I've hit Enter,
recall, as in past classes,

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I proposed that the shortest version
of the URL that you might see

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in your browser upon
searching for cats is this,

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https://www.google.com/search?q=cats.

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Now, that is what you'd
see in your URL bar.

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Below that, you'd see the 10, or the
20, or the 30, or the six billion,

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240 million cats, each of which
has a link that when clicked,

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leads you to a search result.

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But the implication of this
HTTP header is that by default,

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perhaps, unbeknownst to
you, indeed, your browser

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is telling the whole
world from which web page

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you came when you visited some
other web page via a link.

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Now, why in the world
is this compelling?

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Well, it's actually useful for the
website at which you end because it

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might be useful for their analytics.

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They might want to know, well,
how are people finding my website?

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How are people finding my
business on the internet?

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Oh.

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It looks like I'm
getting a lot of users,

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a lot of customers,
perhaps, from google.com,

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specifically, when someone searches
for cats, not dogs, not something else,

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but cats.

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So you can imagine, especially
in the world of commerce,

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that just being useful information
to know how people are finding you,

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or conversely, how people are
not apparently finding you.

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But this is very invasive
because now this website,

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even though it's arguably
none of their business,

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they know I use Google instead of Bing
or some other search engine, perhaps.

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And you can imagine that there could
be links on CS50's own website,

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on any number of other
websites in the world.

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And just because you happened to
visit them and you clicked a link,

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now they're broadcasting your
business to whatever website

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you're ending up on by revealing
where you came from, from where

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you were referred, so to speak.

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But this is long been a feature of HTTP.

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And this has long been a feature that's
enabled by default, unless the website,

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or perhaps, you, as the user, turn this
off or somehow moderate its response.

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Now, some of you might be noticing that
there's a bit of a typo on the screen.

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And I promise, this isn't actually mine.

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In English, at least, this is not
typically how you spell the word,

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referrer.

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And this is actually a fun fact.

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In referrer, there should
be four R's in total.

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It should be R-E-F-E-R-R-E-R.
However, fun fact, years ago,

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when the specification for this
standard was being written,

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the poor individual who wrote the
specification made a typo that has been

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immortalized in history
for years to come.

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And so this is what browsers and
servers have been using and expecting

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for years.

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There are other variants of this header
that these typographical error has

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been fixed in.

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But it's sort of a fun fact
from our internet history.

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But this is, indeed, what you might see
going from your browser to your server.

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So ideally, we'd send less
information, at least.

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I'd be a little more
comfortable if example.com,

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which is this website for
cats, told them, OK, fine.

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I came from Google.

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That's not a big deal.

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But I'd rather you not
know what I was looking for

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if only because that seems unnecessary.

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It seems invasive.

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And who knows what kinds
of cats I was looking for?

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Maybe I don't want you to know exactly
what my preferences are in cats,

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or dogs, or whatever types
of breeds there might be

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in this case of searching for animals.

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So it just feels like it's
unnecessary information to share.

234
00:11:55,770 --> 00:11:58,020
But better still, I
dare say, would not be

235
00:11:58,020 --> 00:12:01,350
to even tell example.com
where I'm coming from

236
00:12:01,350 --> 00:12:04,510
and essentially just get
rid of this altogether.

237
00:12:04,510 --> 00:12:08,250
So how might a website
go about moderating

238
00:12:08,250 --> 00:12:11,460
just how much output comes from the
browsers at the server's request?

239
00:12:11,460 --> 00:12:13,830
Or maybe, how might you
with special software

240
00:12:13,830 --> 00:12:17,160
suppress some of this information to
preserve all the more of your privacy

241
00:12:17,160 --> 00:12:18,810
and what it is you're doing online?

242
00:12:18,810 --> 00:12:23,160
Well, for instance, this is
a common tag that web pages

243
00:12:23,160 --> 00:12:27,690
can put in their own HTML code
that indicates to the browser

244
00:12:27,690 --> 00:12:32,310
that, yes, you may send the referring
address, but only send the origin,

245
00:12:32,310 --> 00:12:36,540
that is, https://www.google.com/.

246
00:12:36,540 --> 00:12:43,230
And that's it, no
search, path, no ?q=cats.

247
00:12:43,230 --> 00:12:46,740
Tell them the website you came from,
but not the specific page or not

248
00:12:46,740 --> 00:12:49,600
the specific search
query or search results.

249
00:12:49,600 --> 00:12:53,040
Notice here in the world of HTML, the
typographical error has been fixed.

250
00:12:53,040 --> 00:12:54,670
There's two R's in the middle there.

251
00:12:54,670 --> 00:12:58,710
But otherwise, this is an
HTML solution to the problem.

252
00:12:58,710 --> 00:13:01,860
The browser, assuming
it respects this HTML,

253
00:13:01,860 --> 00:13:05,280
will therefore, send
and refer HTTP header,

254
00:13:05,280 --> 00:13:10,020
but with less information, not the whole
URL, but just the origin, so really,

255
00:13:10,020 --> 00:13:13,980
the domain name, itself,
and a bit more the protocol.

256
00:13:13,980 --> 00:13:17,670
If you don't want any of that to be
sent for your users, for your customers

257
00:13:17,670 --> 00:13:18,802
you could do this instead.

258
00:13:18,802 --> 00:13:20,010
Now, Google does not do this.

259
00:13:20,010 --> 00:13:24,030
Google currently actually sends
origin, so part of the URL.

260
00:13:24,030 --> 00:13:26,190
But if you want to be
an even better citizen

261
00:13:26,190 --> 00:13:29,820
and not make it easy for browsers to
send more information than they need

262
00:13:29,820 --> 00:13:32,760
to, you can include
this HTML in your page

263
00:13:32,760 --> 00:13:35,850
instead, informing the
browser that you can send--

264
00:13:35,850 --> 00:13:40,470
don't send a referrer at all because
the value of this meta tag, so to speak,

265
00:13:40,470 --> 00:13:43,410
is actually none instead of origin.

266
00:13:43,410 --> 00:13:46,140
And there are other values
as well that allow you

267
00:13:46,140 --> 00:13:48,870
a bit of range of opportunities
when it comes to these settings.

268
00:13:48,870 --> 00:13:52,980
But these are, perhaps, the
most common or ones to consider.

269
00:13:52,980 --> 00:13:54,240
There's an alternative too.

270
00:13:54,240 --> 00:13:56,032
If you happen to be a
little more technical

271
00:13:56,032 --> 00:14:00,360
and you have control over the web server
and not just the HTML on the server,

272
00:14:00,360 --> 00:14:05,430
you can actually configure a
referrer policy, HTTP header,

273
00:14:05,430 --> 00:14:09,640
that goes from the
browserver to the browser.

274
00:14:09,640 --> 00:14:12,510
So in this case, the
referrer policy can indicate

275
00:14:12,510 --> 00:14:16,260
that you only want the origin to
be sent, for instance, the shorter

276
00:14:16,260 --> 00:14:17,400
form of the URL.

277
00:14:17,400 --> 00:14:20,910
Or you can actually indicate
that no referrer should actually

278
00:14:20,910 --> 00:14:24,270
be sent in this particular
case, so a second mechanism

279
00:14:24,270 --> 00:14:26,400
for actually controlling the same.

280
00:14:26,400 --> 00:14:31,190
Let me pause here and see if there's
not only some concerns, perhaps,

281
00:14:31,190 --> 00:14:32,940
now that you understand
better, hopefully,

282
00:14:32,940 --> 00:14:37,800
how the web works, at least, by
default or how we might mitigate

283
00:14:37,800 --> 00:14:40,080
this concern with your privacy.

284
00:14:40,080 --> 00:14:43,350
AUDIENCE: Is there a
way that is easy enough

285
00:14:43,350 --> 00:14:49,110
for us to delete those
traces as a client in case

286
00:14:49,110 --> 00:14:51,595
that we don't want to be
tracked or something like that?

287
00:14:51,595 --> 00:14:53,220
DAVID J. MALAN: A really good question.

288
00:14:53,220 --> 00:14:57,870
We'll refer you to some URLs outside
of the context of class, itself.

289
00:14:57,870 --> 00:15:00,240
But yes, there is actually
client-side software

290
00:15:00,240 --> 00:15:02,520
that you can install
on your own Mac or PC,

291
00:15:02,520 --> 00:15:05,340
typically, that will scrub
some of this information,

292
00:15:05,340 --> 00:15:09,210
so that when your HTTP requests you
go from your browser to servers,

293
00:15:09,210 --> 00:15:12,330
you can ensure that this
third-party software removes

294
00:15:12,330 --> 00:15:15,750
a lot of that information automatically
for you because in that way,

295
00:15:15,750 --> 00:15:19,130
you don't have to trust that the
website, like the Googles of the world

296
00:15:19,130 --> 00:15:22,500
will actually reduce the
amount of information for you.

297
00:15:22,500 --> 00:15:25,250
You can instead do that for yourself
through client-side software.

298
00:15:25,250 --> 00:15:28,100
And we'll provide a few links online.

299
00:15:28,100 --> 00:15:29,990
Other questions on the same?

300
00:15:29,990 --> 00:15:33,160
AUDIENCE: By using a
private browser such as Tor,

301
00:15:33,160 --> 00:15:36,980
for example, or using a temporary
operating system like Tails,

302
00:15:36,980 --> 00:15:40,040
does this remove all of
our traces on the internet?

303
00:15:40,040 --> 00:15:43,157
Or does it leave some on the
client side or the server side?

304
00:15:43,157 --> 00:15:44,490
DAVID J. MALAN: A good question.

305
00:15:44,490 --> 00:15:47,330
Short answer is that it does leave
some evidence on both the server

306
00:15:47,330 --> 00:15:48,680
side and the client side.

307
00:15:48,680 --> 00:15:52,590
But we'll come back to Tor
in just a little bit as well.

308
00:15:52,590 --> 00:15:53,090
All right.

309
00:15:53,090 --> 00:15:54,320
How about one final question?

310
00:15:54,320 --> 00:15:58,430
AUDIENCE: You said previously about
the third-party software that's

311
00:15:58,430 --> 00:16:02,210
supposed to be used in order to scrub
the information from being submitted

312
00:16:02,210 --> 00:16:04,190
to the server side.

313
00:16:04,190 --> 00:16:07,970
What if that program,
itself, is used to eavesdrop

314
00:16:07,970 --> 00:16:10,895
on what we do on the computer?

315
00:16:10,895 --> 00:16:12,770
DAVID J. MALAN: That is
a very valid concern.

316
00:16:12,770 --> 00:16:14,690
It is absolutely possible.

317
00:16:14,690 --> 00:16:17,540
In general, what is
working in your favor

318
00:16:17,540 --> 00:16:20,840
is either open-source software,
where if you're using software

319
00:16:20,840 --> 00:16:23,840
that other people can see the
source code of, presumably,

320
00:16:23,840 --> 00:16:26,210
it's less likely that it's
doing something malicious.

321
00:16:26,210 --> 00:16:29,090
Capitalism often helps
you here too, whereby,

322
00:16:29,090 --> 00:16:32,000
it is often not in a
company's own interest

323
00:16:32,000 --> 00:16:35,320
to be violating the privacy of
their users because presumably,

324
00:16:35,320 --> 00:16:38,570
that would create some form of backlash,
which would not be good for business.

325
00:16:38,570 --> 00:16:41,240
But beyond that, there is
a lot of trust on your part

326
00:16:41,240 --> 00:16:44,240
and my part whenever it
comes to installing software.

327
00:16:44,240 --> 00:16:46,850
So that is, indeed, very much a risk.

328
00:16:46,850 --> 00:16:48,980
Now, it turns out
there's other information

329
00:16:48,980 --> 00:16:52,100
that your browser might be
sharing without your realizing

330
00:16:52,100 --> 00:16:53,390
that it's making it available.

331
00:16:53,390 --> 00:16:57,260
And that information is enough
via which servers can even

332
00:16:57,260 --> 00:16:58,820
fingerprint you, so to speak.

333
00:16:58,820 --> 00:17:01,070
That is to say there's this
technique generally called

334
00:17:01,070 --> 00:17:03,230
fingerprinting that in
the context of the web

335
00:17:03,230 --> 00:17:07,310
means to take as input a
whole bunch of characteristics

336
00:17:07,310 --> 00:17:09,859
of the request from the
internet that's coming in

337
00:17:09,859 --> 00:17:14,060
and see if you can use those
characteristics to create

338
00:17:14,060 --> 00:17:17,869
a profile of sorts for the
user via which you can uniquely

339
00:17:17,869 --> 00:17:19,440
identify that user.

340
00:17:19,440 --> 00:17:22,579
Now, that doesn't mean you'll know
specifically that user is David Malan.

341
00:17:22,579 --> 00:17:25,550
But you will know,
according to this system,

342
00:17:25,550 --> 00:17:28,790
if it's the same user
today, as you see tomorrow,

343
00:17:28,790 --> 00:17:32,690
as you see the next day because
you can use this information

344
00:17:32,690 --> 00:17:36,770
to infer with high probability that,
OK, we saw that exact same browser

345
00:17:36,770 --> 00:17:39,050
configuration again,
and again, and again.

346
00:17:39,050 --> 00:17:42,170
Odds are it's the same
person and not some twin

347
00:17:42,170 --> 00:17:45,150
on the internet who just happens
to have precisely those settings.

348
00:17:45,150 --> 00:17:48,260
Now, how might this be implemented
or achieved technologically?

349
00:17:48,260 --> 00:17:50,360
Well, the simplest
mechanism, perhaps, is just

350
00:17:50,360 --> 00:17:52,190
to rely on something
like your IP address.

351
00:17:52,190 --> 00:17:54,830
Recall that any time you're
doing something on the internet,

352
00:17:54,830 --> 00:17:57,110
those virtual envelopes
we keep talking about

353
00:17:57,110 --> 00:18:00,480
have your IP address on
the outside, so to speak,

354
00:18:00,480 --> 00:18:03,470
as well as the IP address of
the destination to which you're

355
00:18:03,470 --> 00:18:04,820
trying to send information.

356
00:18:04,820 --> 00:18:07,080
Your IP, in that case,
is the return address,

357
00:18:07,080 --> 00:18:10,010
which means you're literally
telling the remote server when

358
00:18:10,010 --> 00:18:13,190
using certain protocols
where you are in the world,

359
00:18:13,190 --> 00:18:15,050
or at least, what your IP address is.

360
00:18:15,050 --> 00:18:18,320
Now, that IP address might not
alone uniquely identify you

361
00:18:18,320 --> 00:18:22,700
because it turns out on campuses,
in homes, in corporate networks,

362
00:18:22,700 --> 00:18:26,390
you might actually share one IP
address with many other people,

363
00:18:26,390 --> 00:18:30,090
but at least narrows the
scope of whose IP it might be,

364
00:18:30,090 --> 00:18:31,970
even if it's shared among a few people.

365
00:18:31,970 --> 00:18:34,940
But your browser inside
of that virtual envelope

366
00:18:34,940 --> 00:18:37,200
is sharing other information as well.

367
00:18:37,200 --> 00:18:42,350
Another HTTP header that is
typically sent by browsers to servers

368
00:18:42,350 --> 00:18:43,940
is called user agent.

369
00:18:43,940 --> 00:18:48,380
And this is just a unique string of
text that uniquely identifies typically

370
00:18:48,380 --> 00:18:52,310
the browser that you're using and
the version thereof and the operating

371
00:18:52,310 --> 00:18:54,530
system that you're using
and the version thereof.

372
00:18:54,530 --> 00:18:58,052
So for instance, a standard format
might look a little something like this.

373
00:18:58,052 --> 00:18:59,510
And it's deliberately overwhelming.

374
00:18:59,510 --> 00:19:01,880
And it's just meant to
capture how much detail

375
00:19:01,880 --> 00:19:04,040
might be leaked in this header's value.

376
00:19:04,040 --> 00:19:06,740
But within this big string
of text that doesn't even

377
00:19:06,740 --> 00:19:09,740
fit onto one line-- it's wrapping
here under three lines-- is

378
00:19:09,740 --> 00:19:13,400
some indication of what browser you're
using, be it, Chrome or something else

379
00:19:13,400 --> 00:19:15,620
and what operating system
you're using, be it,

380
00:19:15,620 --> 00:19:19,520
Android or something else on a
phone, a laptop, or a desktop.

381
00:19:19,520 --> 00:19:21,710
Now, of course, a lot
of people in the world

382
00:19:21,710 --> 00:19:23,870
presumably have the
same browser installed.

383
00:19:23,870 --> 00:19:26,600
So that, too, even with
IP address, might not

384
00:19:26,600 --> 00:19:30,140
be enough information to
uniquely identify you,

385
00:19:30,140 --> 00:19:31,530
at least, with high probability.

386
00:19:31,530 --> 00:19:33,720
So what else can servers do?

387
00:19:33,720 --> 00:19:37,970
Well, if the server has the ability
to send some code to your computer,

388
00:19:37,970 --> 00:19:41,330
for instance, some HTML, some
CSS, and some JavaScript,

389
00:19:41,330 --> 00:19:45,710
servers can effectively interrogate the
browser and ask it certain questions.

390
00:19:45,710 --> 00:19:50,768
For instance, a server could figure out
what the resolution is of your screen.

391
00:19:50,768 --> 00:19:53,060
Now, this might be practically
useful, so they know how

392
00:19:53,060 --> 00:19:54,900
to render information on the screen.

393
00:19:54,900 --> 00:19:56,610
But that alone might be enough.

394
00:19:56,610 --> 00:20:00,410
Especially if you're in the habit
of full screening your browser

395
00:20:00,410 --> 00:20:03,260
and you always use the same
resolution on your monitor,

396
00:20:03,260 --> 00:20:07,070
that might be another ingredient with
which to identify or fingerprint you.

397
00:20:07,070 --> 00:20:09,890
The server might be able
to figure out what fonts

398
00:20:09,890 --> 00:20:12,170
you have installed on your system.

399
00:20:12,170 --> 00:20:14,750
The server might be able
to figure out what time

400
00:20:14,750 --> 00:20:18,950
zone you are in because that's also
a value available within the context

401
00:20:18,950 --> 00:20:19,760
of a browser.

402
00:20:19,760 --> 00:20:24,470
And there's yet other values still
that collectively with high probability

403
00:20:24,470 --> 00:20:26,760
can be used to fingerprint you and me.

404
00:20:26,760 --> 00:20:29,390
So even if you're not even
logged in, even if you're

405
00:20:29,390 --> 00:20:32,990
using various privacy enhancing
software products to try

406
00:20:32,990 --> 00:20:35,330
to remove some of these
HTTP headers and the like,

407
00:20:35,330 --> 00:20:39,680
you're still leaking other information,
including the extensions or plug-ins,

408
00:20:39,680 --> 00:20:42,690
sometimes, that your browser
might have installed.

409
00:20:42,690 --> 00:20:45,983
So if you're in the habit of using
the same computer again and again

410
00:20:45,983 --> 00:20:48,650
and you're in the habit of not
changing a lot of these settings,

411
00:20:48,650 --> 00:20:52,070
that alone might be enough for a
website to effectively track you.

412
00:20:52,070 --> 00:20:53,420
Now, it might be innocuous.

413
00:20:53,420 --> 00:20:55,520
They might just use this
for statistical purposes

414
00:20:55,520 --> 00:20:58,010
to get a sense of how many
users or customers they have.

415
00:20:58,010 --> 00:21:00,050
But it could be for
more invasive purposes,

416
00:21:00,050 --> 00:21:02,330
like serving you targeted
advertising, based

417
00:21:02,330 --> 00:21:05,450
on your behavior of these websites,
or really, just tracking you,

418
00:21:05,450 --> 00:21:06,260
specifically.

419
00:21:06,260 --> 00:21:09,740
And the catch is that if you
ever log in to this server

420
00:21:09,740 --> 00:21:13,820
just once, if the server has been
logging all of your traffic based

421
00:21:13,820 --> 00:21:17,510
on that fingerprint for days, for
months, for years, at that point,

422
00:21:17,510 --> 00:21:20,870
retroactively, with high probability,
they can infer, oh, wait a minute.

423
00:21:20,870 --> 00:21:23,570
If the user on this day
was David and we think

424
00:21:23,570 --> 00:21:27,080
it was the same user on all of these
previous days, now by transitivity,

425
00:21:27,080 --> 00:21:30,810
they know a lot more about
your browser history as well.

426
00:21:30,810 --> 00:21:34,460
So even unbeknownst to you, and
even without explicit header values

427
00:21:34,460 --> 00:21:37,940
being sent that identify
you, the collection

428
00:21:37,940 --> 00:21:41,360
of attributes or characteristics
that our browsers have

429
00:21:41,360 --> 00:21:45,530
and our browsing behavior has can
still be enough to uniquely identify

430
00:21:45,530 --> 00:21:47,570
most of us quite a bit of the time.

431
00:21:47,570 --> 00:21:51,080
Let me pause here and see if there's
any questions on fingerprinting

432
00:21:51,080 --> 00:21:54,560
or these implications for privacy.

433
00:21:54,560 --> 00:21:58,897
AUDIENCE: Will using a VPN
prevent browser fingerprinting?

434
00:21:58,897 --> 00:22:00,230
DAVID J. MALAN: A good question.

435
00:22:00,230 --> 00:22:02,570
And we'll talk about
VPNs a bit more soon.

436
00:22:02,570 --> 00:22:03,650
Short answer, no.

437
00:22:03,650 --> 00:22:07,490
So VPNs will typically mask your
IP address, but that's about it.

438
00:22:07,490 --> 00:22:12,115
If you still use your browser as
usual with your user account as usual,

439
00:22:12,115 --> 00:22:14,240
all of that same information
is going to be leaked.

440
00:22:14,240 --> 00:22:16,850
It's just going to
change one piece of it.

441
00:22:16,850 --> 00:22:18,090
A good question.

442
00:22:18,090 --> 00:22:20,645
Other questions on
fingerprinting and privacy?

443
00:22:20,645 --> 00:22:24,980
AUDIENCE: Is it possible that a
hacker can steal a fingerprint

444
00:22:24,980 --> 00:22:28,670
and use it for their own
purposes and everything

445
00:22:28,670 --> 00:22:33,100
will look like it was my computer
that performed certain actions?

446
00:22:33,100 --> 00:22:36,695
so it's like stealing an identity.

447
00:22:36,695 --> 00:22:38,810
DAVID J. MALAN: A short
answer, yes, if the hacker

448
00:22:38,810 --> 00:22:40,760
has access to the same information.

449
00:22:40,760 --> 00:22:43,580
If though, if we rewind
to our focus on encryption

450
00:22:43,580 --> 00:22:46,910
a couple of classes ago, if
you are accessing websites only

451
00:22:46,910 --> 00:22:50,870
via HTTPS and nothing is
unencrypted, then it's

452
00:22:50,870 --> 00:22:54,320
going to be a lot harder for a
hacker in between you and that server

453
00:22:54,320 --> 00:22:58,130
to glean any of the same information
because almost all of it is encrypted.

454
00:22:58,130 --> 00:22:59,360
IP address is not.

455
00:22:59,360 --> 00:23:04,140
But anything inside of the envelope
is, including these headers, the HTML,

456
00:23:04,140 --> 00:23:05,900
the JavaScript, and the CSS.

457
00:23:05,900 --> 00:23:08,240
If, though, the hacker
has somehow infiltrated

458
00:23:08,240 --> 00:23:13,070
your own laptop, or desktop, or phone,
or the server, then all bets are off.

459
00:23:13,070 --> 00:23:15,590
And they could absolutely
identify you, according

460
00:23:15,590 --> 00:23:18,730
to these same pieces of information.

461
00:23:18,730 --> 00:23:19,796
Other questions?

462
00:23:19,796 --> 00:23:22,780
AUDIENCE: I was just curious to
understand the difference, perhaps,

463
00:23:22,780 --> 00:23:24,310
when you are on mobile.

464
00:23:24,310 --> 00:23:28,150
My understanding is that they can
even get much more information

465
00:23:28,150 --> 00:23:29,915
when you are on mobile.

466
00:23:29,915 --> 00:23:31,540
DAVID J. MALAN: That's a fair question.

467
00:23:31,540 --> 00:23:34,030
I don't think I would
answer yes to that.

468
00:23:34,030 --> 00:23:38,680
I'm hard pressed to imagine what more
your phone is doing than the browser is

469
00:23:38,680 --> 00:23:41,800
doing, except that there are--

470
00:23:41,800 --> 00:23:44,500
I suppose I could argue
that your phone tends

471
00:23:44,500 --> 00:23:49,990
to have additional features nowadays,
like GPS, like accelerometers,

472
00:23:49,990 --> 00:23:53,740
gyroscope, perhaps, so other
hardware features that theoretically

473
00:23:53,740 --> 00:23:57,530
can be interrogated by JavaScript
code, typically, on an opt-in basis.

474
00:23:57,530 --> 00:24:00,790
So you, the user, could deny access
to these pieces of information.

475
00:24:00,790 --> 00:24:03,820
But those characteristics,
I suspect could

476
00:24:03,820 --> 00:24:08,260
be used to identify you a bit more
uniquely because laptops, at least,

477
00:24:08,260 --> 00:24:11,538
today, have less of that functionality.

478
00:24:11,538 --> 00:24:12,205
Other questions?

479
00:24:12,205 --> 00:24:17,350
AUDIENCE: When storing and
retrieving data on the front end,

480
00:24:17,350 --> 00:24:24,125
is it more secure to use cookies,
local storage, or another alternative?

481
00:24:24,125 --> 00:24:25,750
DAVID J. MALAN: A really good question.

482
00:24:25,750 --> 00:24:29,500
And we will come to this subject
literally in one slide, cookies.

483
00:24:29,500 --> 00:24:32,200
In general, local
storage because cookies,

484
00:24:32,200 --> 00:24:34,960
by design, are meant to be sent
back and forth, back and forth

485
00:24:34,960 --> 00:24:36,700
between browser and server.

486
00:24:36,700 --> 00:24:39,940
Theoretically, that should not be a
concern if everything is encrypted.

487
00:24:39,940 --> 00:24:43,060
But we've talked in the past
already how mistakes can be made.

488
00:24:43,060 --> 00:24:46,360
You might start on HTTP,
be redirected to HTTPS.

489
00:24:46,360 --> 00:24:49,360
So in general, storing things
in local storage, at least,

490
00:24:49,360 --> 00:24:52,840
prevent things from accidentally
leaking out over the browser connection.

491
00:24:52,840 --> 00:24:55,900
That said, if you're storing
things in local storage,

492
00:24:55,900 --> 00:24:57,770
they are literally available locally.

493
00:24:57,770 --> 00:25:00,160
So if you have a colleague,
a friend, a sibling

494
00:25:00,160 --> 00:25:04,000
who gains physical access to that
device, let alone, an adversary,

495
00:25:04,000 --> 00:25:07,330
then they could see all of the
information and not only your cookies,

496
00:25:07,330 --> 00:25:09,100
but also local storage.

497
00:25:09,100 --> 00:25:11,890
So at that point, physical
access, generally,

498
00:25:11,890 --> 00:25:15,170
all bets are off when it
comes to your privacy.

499
00:25:15,170 --> 00:25:15,670
All right.

500
00:25:15,670 --> 00:25:17,670
How about one other question?

501
00:25:17,670 --> 00:25:22,300
AUDIENCE: There were calls being made
from people's local phone numbers

502
00:25:22,300 --> 00:25:25,540
on cell phones to other local numbers.

503
00:25:25,540 --> 00:25:27,710
Obviously, the people
weren't making the calls.

504
00:25:27,710 --> 00:25:28,960
And it had happened to me too.

505
00:25:28,960 --> 00:25:31,540
And I was wondering
how that kind of works

506
00:25:31,540 --> 00:25:34,000
or if it's related to this at all.

507
00:25:34,000 --> 00:25:35,298
DAVID J. MALAN: It is.

508
00:25:35,298 --> 00:25:37,090
We weren't planning to
talk about it today.

509
00:25:37,090 --> 00:25:41,380
But in a nutshell, it is very
easy to spoof telephone numbers.

510
00:25:41,380 --> 00:25:44,440
And this is how a lot of spam
calls are sent, particularly,

511
00:25:44,440 --> 00:25:46,540
internationally or abroad,
where they might not

512
00:25:46,540 --> 00:25:49,510
be regulated in the same way
as someone's home country.

513
00:25:49,510 --> 00:25:53,590
It's very common, too, for
if your number starts--

514
00:25:53,590 --> 00:25:57,820
your own phone number starts with
555, for instance, very often, you'll

515
00:25:57,820 --> 00:26:01,120
get fake calls from
other numbers that also

516
00:26:01,120 --> 00:26:03,850
start with 555 because the
presumption by the adversary

517
00:26:03,850 --> 00:26:06,790
is that, oh, Sabrina's probably
more likely to pick this up

518
00:26:06,790 --> 00:26:09,910
if she thinks it's a neighbor with
a similar looking phone number.

519
00:26:09,910 --> 00:26:11,860
But unfortunately,
with the phone system,

520
00:26:11,860 --> 00:26:13,960
it's all too easy to fake phone numbers.

521
00:26:13,960 --> 00:26:17,480
And this is yet another reason
why using phones, using SMS,

522
00:26:17,480 --> 00:26:20,030
is not a recommended approach
for our earlier topic

523
00:26:20,030 --> 00:26:21,890
about multi-factor authentication.

524
00:26:21,890 --> 00:26:23,390
It's just not a secure network.

525
00:26:23,390 --> 00:26:27,230
That's not how Edison and others
designed it 100-plus years ago.

526
00:26:27,230 --> 00:26:30,890
This is why systems that use
cryptography in some form

527
00:26:30,890 --> 00:26:35,020
are much safer when it
comes to that information.

528
00:26:35,020 --> 00:26:35,650
All right.

529
00:26:35,650 --> 00:26:38,020
So beyond this user
agent header, there's

530
00:26:38,020 --> 00:26:42,032
other headers that your browser is often
sending back and forth with the server.

531
00:26:42,032 --> 00:26:44,240
And one of these we've talked
about, and one of these

532
00:26:44,240 --> 00:26:47,020
you probably came into the course
knowing about, namely, cookies.

533
00:26:47,020 --> 00:26:48,728
But there are different
types of cookies.

534
00:26:48,728 --> 00:26:51,700
But recall that in general, a
cookie is a piece of information

535
00:26:51,700 --> 00:26:56,360
that a server puts on your computer
to help remember who you are.

536
00:26:56,360 --> 00:26:59,020
So in the absence of these
fingerprints and the absence

537
00:26:59,020 --> 00:27:01,060
of specific headers
like these, it can just

538
00:27:01,060 --> 00:27:04,685
put a small random value
with numbers and letters

539
00:27:04,685 --> 00:27:07,060
or the like on your computer
or maybe even a bigger value

540
00:27:07,060 --> 00:27:08,140
if it has lots of users.

541
00:27:08,140 --> 00:27:11,290
And it uses that value
to uniquely identify you

542
00:27:11,290 --> 00:27:14,350
if you return again and
again to the website.

543
00:27:14,350 --> 00:27:16,720
It doesn't necessarily
know that I am David,

544
00:27:16,720 --> 00:27:19,265
unless I log in at some
point, at which point,

545
00:27:19,265 --> 00:27:20,890
then it can realize, oh, wait a minute.

546
00:27:20,890 --> 00:27:22,670
David's cookie is this value.

547
00:27:22,670 --> 00:27:24,942
Now I know who this user is.

548
00:27:24,942 --> 00:27:26,650
But in general, there
are different types

549
00:27:26,650 --> 00:27:28,660
of cookies and different
settings for cookies that are

550
00:27:28,660 --> 00:27:30,285
worth knowing a little something about.

551
00:27:30,285 --> 00:27:34,000
So we talked previously about what we'd
more properly call session cookies.

552
00:27:34,000 --> 00:27:39,000
So session cookies are used
by servers to maintain state,

553
00:27:39,000 --> 00:27:41,600
so to speak, between the
server and the browser.

554
00:27:41,600 --> 00:27:46,280
That is to say, without getting too
technical, HTTP is typically stateless,

555
00:27:46,280 --> 00:27:49,550
whereby, when you visit a page, the
browser icon might spin for a bit.

556
00:27:49,550 --> 00:27:52,310
And then it stops because the
transaction between the browser

557
00:27:52,310 --> 00:27:54,420
and the server is complete.

558
00:27:54,420 --> 00:27:58,100
But if you want to remember
who the user is, therefore,

559
00:27:58,100 --> 00:28:01,970
the second, the third, the fourth
time, the browser contacts the server.

560
00:28:01,970 --> 00:28:05,000
The browser had better
remind the server who it is.

561
00:28:05,000 --> 00:28:08,710
And this is why we use the metaphor
of the virtual handstamp, whereby,

562
00:28:08,710 --> 00:28:11,210
that handstamp is the browser's
way of reminding the server,

563
00:28:11,210 --> 00:28:12,200
you've seen me before.

564
00:28:12,200 --> 00:28:13,710
Don't make me log in again.

565
00:28:13,710 --> 00:28:14,810
I am David.

566
00:28:14,810 --> 00:28:15,770
I am David.

567
00:28:15,770 --> 00:28:18,950
--even though it's just relying on
this virtual handstamp or really

568
00:28:18,950 --> 00:28:23,720
some unique identifier that's going
in the cookie header from browser

569
00:28:23,720 --> 00:28:24,510
to server.

570
00:28:24,510 --> 00:28:26,870
So a session cookie allows
browsers and servers

571
00:28:26,870 --> 00:28:29,390
to maintain sessions,
this kind of state.

572
00:28:29,390 --> 00:28:33,230
A little more concretely, it allows them
to maintain things like shopping carts.

573
00:28:33,230 --> 00:28:35,907
So if you're shopping on
an amazon.com or the like,

574
00:28:35,907 --> 00:28:39,230
the session cookie is what
remembers who you are,

575
00:28:39,230 --> 00:28:41,900
or at least, that you're the same
person, so that every time you

576
00:28:41,900 --> 00:28:45,680
poke around on the website, Amazon shows
you the same contents of your shopping

577
00:28:45,680 --> 00:28:47,870
cart again and again,
so that they don't lose

578
00:28:47,870 --> 00:28:51,630
your business by accidentally deleting
it when you simply change the page.

579
00:28:51,630 --> 00:28:53,510
So how do session cookies work?

580
00:28:53,510 --> 00:28:55,670
Well, when you first
visit a website that

581
00:28:55,670 --> 00:28:58,640
wants to plant a cookie
on your computer,

582
00:28:58,640 --> 00:29:01,100
the response might look a
little something like this.

583
00:29:01,100 --> 00:29:01,970
HTTP.

584
00:29:01,970 --> 00:29:04,820
200 is the status code,
which, recall, means OK.

585
00:29:04,820 --> 00:29:05,630
All is well.

586
00:29:05,630 --> 00:29:08,820
It's not something like 404,
which would mean file not found.

587
00:29:08,820 --> 00:29:10,190
So 200 is OK.

588
00:29:10,190 --> 00:29:14,660
But the server might also respond with
this key value pair, this HTTP header,

589
00:29:14,660 --> 00:29:16,890
Set-Cookie:.

590
00:29:16,890 --> 00:29:17,970
So that's the key.

591
00:29:17,970 --> 00:29:22,220
The value of which is session=1234abcd.

592
00:29:22,220 --> 00:29:24,260
And that's the same
value we used previously

593
00:29:24,260 --> 00:29:26,390
when we talked about
cookies in this context.

594
00:29:26,390 --> 00:29:30,140
And the point here is that the
name of this cookie is Session.

595
00:29:30,140 --> 00:29:34,790
And its value equals,
in this case, 1234abcd.

596
00:29:34,790 --> 00:29:37,970
Now, if you visit the same
website and you, and you, and you,

597
00:29:37,970 --> 00:29:42,110
we would all have different seemingly
random values for those cookies.

598
00:29:42,110 --> 00:29:45,283
And so this number, this
sequence of letters and numbers,

599
00:29:45,283 --> 00:29:46,700
would be different for each of us.

600
00:29:46,700 --> 00:29:49,070
That is to say we have
different handstamps

601
00:29:49,070 --> 00:29:50,940
that we're presenting each time.

602
00:29:50,940 --> 00:29:52,830
Now, this is a session cookie.

603
00:29:52,830 --> 00:29:55,550
And it's a session cookie
in the sense that it

604
00:29:55,550 --> 00:29:59,300
is supposed to expire when
you close the browser, when

605
00:29:59,300 --> 00:30:02,912
you quit for the night, when
you reboot or anything else.

606
00:30:02,912 --> 00:30:05,120
Now, with that said, that's
a bit of an overstatement

607
00:30:05,120 --> 00:30:09,652
because browsers nowadays will
frequently preserve your tabs for you.

608
00:30:09,652 --> 00:30:10,610
They might go to sleep.

609
00:30:10,610 --> 00:30:12,110
You might have to wake them back up.

610
00:30:12,110 --> 00:30:15,110
But increasingly, sessions are
living longer than they once did.

611
00:30:15,110 --> 00:30:20,000
But the idea is that this is not
meant to last for a year or forever.

612
00:30:20,000 --> 00:30:24,230
It has a much shorter
lifetime by design.

613
00:30:24,230 --> 00:30:28,490
When your browser has received that
cookie and you click on some other

614
00:30:28,490 --> 00:30:31,280
page, you visit some other
product on amazon.com,

615
00:30:31,280 --> 00:30:35,630
your browser might say something
like this, GET/ and then cookie:,

616
00:30:35,630 --> 00:30:37,080
that exact same value.

617
00:30:37,080 --> 00:30:38,930
So recall from our
previous class, this is

618
00:30:38,930 --> 00:30:43,340
how the browser just reminds
the server what its handstamp is

619
00:30:43,340 --> 00:30:44,900
or what its cookie value is.

620
00:30:44,900 --> 00:30:48,350
But again, the idea is that
when the browser is closed,

621
00:30:48,350 --> 00:30:51,920
you reboot for the night,
then you should not

622
00:30:51,920 --> 00:30:56,490
have the same session cookie
tomorrow, at least, in this model.

623
00:30:56,490 --> 00:30:59,000
That's not true for all websites,
but according to cookies

624
00:30:59,000 --> 00:31:00,680
as we are currently using them.

625
00:31:00,680 --> 00:31:04,160
Now, that's pretty good for your
privacy because if the cookie is

626
00:31:04,160 --> 00:31:08,390
by design meant to be a session cookie
and it expires pretty soon when you're

627
00:31:08,390 --> 00:31:11,510
done with that browser tab or done
using the browser for the day,

628
00:31:11,510 --> 00:31:14,635
then that's pretty good because it
means if you go back to the same website

629
00:31:14,635 --> 00:31:16,830
tomorrow, that cookie
might not exist anymore,

630
00:31:16,830 --> 00:31:19,890
so you might as well look
like or be a brand new user.

631
00:31:19,890 --> 00:31:23,880
So they can't correlate, perhaps, by
default as much information about you.

632
00:31:23,880 --> 00:31:28,070
But these are the cookies that
you read about being bad for you

633
00:31:28,070 --> 00:31:30,740
and bad for your privacy,
tracking cookies, which

634
00:31:30,740 --> 00:31:33,830
are the exact same idea,
key value pairs that

635
00:31:33,830 --> 00:31:37,100
are sent from server to browser to
remember who you are, or at least,

636
00:31:37,100 --> 00:31:39,830
that you're the same person,
even if we don't know that you're

637
00:31:39,830 --> 00:31:42,060
David Malan specifically just yet.

638
00:31:42,060 --> 00:31:44,690
But as per the name,
tracking cookies are really

639
00:31:44,690 --> 00:31:46,830
designed to track you and me.

640
00:31:46,830 --> 00:31:47,330
Why?

641
00:31:47,330 --> 00:31:50,500
Well maybe analytical purposes,
maybe debugging purposes,

642
00:31:50,500 --> 00:31:53,000
so that they know where users
were in case something breaks,

643
00:31:53,000 --> 00:31:55,580
maybe advertising
purposes, so that you get

644
00:31:55,580 --> 00:31:58,760
served different ads from me, so
that they can maximize their revenue

645
00:31:58,760 --> 00:32:01,250
by clickserving up ads
that you and I are each

646
00:32:01,250 --> 00:32:03,120
more individually likely to click on.

647
00:32:03,120 --> 00:32:06,740
So tracking cookies are the ones
that get a bad rep and rightfully so.

648
00:32:06,740 --> 00:32:08,720
So let's consider an
example of a cookie that's

649
00:32:08,720 --> 00:32:11,900
designed to track your behavior
on a particular website.

650
00:32:11,900 --> 00:32:14,540
Here, for instance,
is a set-cookie header

651
00:32:14,540 --> 00:32:18,210
that Google, specifically,
might send to your browser.

652
00:32:18,210 --> 00:32:23,270
In fact, they use a cookie that by
convention is called _ga for Google

653
00:32:23,270 --> 00:32:25,640
Analytics, which they use
for analytical purposes.

654
00:32:25,640 --> 00:32:28,470
And its value looks a
little something like this.

655
00:32:28,470 --> 00:32:31,520
And the point of this value
is that it's generated

656
00:32:31,520 --> 00:32:35,570
on a per website basis if that
website is using Google Analytics.

657
00:32:35,570 --> 00:32:40,220
And Google Analytics is a tool that
allows website designers to track

658
00:32:40,220 --> 00:32:44,240
who is clicking on what, what browsers
they're using, what operating systems

659
00:32:44,240 --> 00:32:47,570
they're using, and generally giving
them a sense of the demographics

660
00:32:47,570 --> 00:32:48,770
of their user base.

661
00:32:48,770 --> 00:32:53,210
But unlike session cookies, which
are meant to expire after a day,

662
00:32:53,210 --> 00:32:57,800
after the browser closes or the
like, Google's analytical cookie here

663
00:32:57,800 --> 00:33:01,310
has a maximum age of this many
seconds, which if you do out

664
00:33:01,310 --> 00:33:05,070
the math is by default two
years, which is to say,

665
00:33:05,070 --> 00:33:09,440
if you visit some website that is
using Google Analytics by embedding

666
00:33:09,440 --> 00:33:13,670
a bit of Google's JavaScript code in
their website, whenever that Google

667
00:33:13,670 --> 00:33:16,070
code is pulled from
Google's website, Google

668
00:33:16,070 --> 00:33:20,090
has an opportunity to plant
this cookie on your computer.

669
00:33:20,090 --> 00:33:24,650
And you'll get a unique ID based
on you visiting for the first time,

670
00:33:24,650 --> 00:33:28,580
based on the specific website that
is embedding Google Analytics.

671
00:33:28,580 --> 00:33:31,340
And that cookie is going
to live in your computer,

672
00:33:31,340 --> 00:33:35,150
according to this HTTP header,
for as long as two years.

673
00:33:35,150 --> 00:33:36,518
Now, that's useful for Google.

674
00:33:36,518 --> 00:33:38,060
It's perhaps, useful for the website.

675
00:33:38,060 --> 00:33:41,240
It's perhaps, a little more
invasive for me and you.

676
00:33:41,240 --> 00:33:43,550
Now, Google has many other
cookies that they use too.

677
00:33:43,550 --> 00:33:46,312
But this is, perhaps, one that
you should keep an eye out for.

678
00:33:46,312 --> 00:33:48,020
And indeed, in the
coming weeks or months

679
00:33:48,020 --> 00:33:50,228
if you poke around some of
your own browser settings,

680
00:33:50,228 --> 00:33:53,930
you might very well
see values like this.

681
00:33:53,930 --> 00:33:57,780
But what else might servers
use to keep track of us,

682
00:33:57,780 --> 00:34:01,040
especially if you and I are in
the habit of deleting our cookies

683
00:34:01,040 --> 00:34:05,552
or clearing your history, which
would be counterproductive for Google

684
00:34:05,552 --> 00:34:07,760
or websites that are trying
to track you in this way,

685
00:34:07,760 --> 00:34:12,358
but a plus for you and for my privacy
if you're behaving in this way?

686
00:34:12,358 --> 00:34:14,150
But it turns out there's
other ways servers

687
00:34:14,150 --> 00:34:18,560
can track us, including through HTTP
parameters, tracking parameters.

688
00:34:18,560 --> 00:34:20,659
So parameters are the
key value pairs that

689
00:34:20,659 --> 00:34:24,560
often appear in URLs that are
sent via GET requests typically.

690
00:34:24,560 --> 00:34:25,699
So we've seen one of these.

691
00:34:25,699 --> 00:34:28,760
If you recall when we searched
for cats on Google before,

692
00:34:28,760 --> 00:34:30,770
you might recall that
the URL was something

693
00:34:30,770 --> 00:34:39,230
like
https://www.google.com/search?q=cats.

694
00:34:39,230 --> 00:34:44,780
Anything after a question mark in a
URL is, indeed, an HTTP parameter.

695
00:34:44,780 --> 00:34:48,380
But it could be used not for innocuous
helpful purposes, like searching

696
00:34:48,380 --> 00:34:50,690
for cats, but also, to track you.

697
00:34:50,690 --> 00:34:52,880
And in fact, if you
see ampersands in URLs,

698
00:34:52,880 --> 00:34:57,190
that might mean that you have a second,
or a third, or more parameter up there.

699
00:34:57,190 --> 00:35:00,120
And sometimes the purpose
of these parameters

700
00:35:00,120 --> 00:35:03,340
is simply to track you as some person.

701
00:35:03,340 --> 00:35:06,330
So for instance, here
is a representative URL.

702
00:35:06,330 --> 00:35:07,320
It's a long one.

703
00:35:07,320 --> 00:35:14,500
And this is taken from example.com
having a path of as_engagement?.

704
00:35:14,500 --> 00:35:19,800
And then I'll highlight here click_id=
and then this long seemingly random

705
00:35:19,800 --> 00:35:20,310
string.

706
00:35:20,310 --> 00:35:24,740
But there's a second HTTP
parameter in this particular URL.

707
00:35:24,740 --> 00:35:27,670
&campaign_id=23.

708
00:35:27,670 --> 00:35:30,660
So the campaign ID, certainly
with such a small number,

709
00:35:30,660 --> 00:35:32,070
is not meant to track you.

710
00:35:32,070 --> 00:35:36,470
That's meant to be sufficient input to
the website to know what types of ads

711
00:35:36,470 --> 00:35:37,470
should be served to you.

712
00:35:37,470 --> 00:35:40,110
What campaign should be served up?

713
00:35:40,110 --> 00:35:44,760
But this click_id, which is sort
of a euphemism for tracking cookie

714
00:35:44,760 --> 00:35:50,040
or tracking parameter in this case, is
what's actually keeping track of you,

715
00:35:50,040 --> 00:35:51,990
specifically, because
different users are

716
00:35:51,990 --> 00:35:54,390
going to find that
whatever link they click on

717
00:35:54,390 --> 00:35:57,570
has a slightly different
value for click_id.

718
00:35:57,570 --> 00:35:59,820
So recall that a tracking
cookie is something

719
00:35:59,820 --> 00:36:01,410
that's sent via an HTTP header.

720
00:36:01,410 --> 00:36:03,243
And so it's harder for
you and me to see it,

721
00:36:03,243 --> 00:36:05,202
unless we're more
comfortable with our browsers

722
00:36:05,202 --> 00:36:07,110
and can poke around some
underlying settings.

723
00:36:07,110 --> 00:36:11,310
But these tracking parameters are
right there in front of you, at least,

724
00:36:11,310 --> 00:36:15,780
if you click on the URL in your browser
and take a look at its entirety.

725
00:36:15,780 --> 00:36:20,310
Now, wonderfully, at least for us end
users who are concerned about privacy,

726
00:36:20,310 --> 00:36:23,700
browsers and even third-party
software are increasingly

727
00:36:23,700 --> 00:36:26,190
removing values like this for us.

728
00:36:26,190 --> 00:36:28,500
As soon as the browser
manufacturer or as soon

729
00:36:28,500 --> 00:36:31,560
as the third-party software
developer knows that, wait a minute,

730
00:36:31,560 --> 00:36:36,930
click ID has no good purpose
other than tracking our users,

731
00:36:36,930 --> 00:36:39,897
they can simply automatically
remove it for you.

732
00:36:39,897 --> 00:36:41,730
After all, when you
visit a web page and you

733
00:36:41,730 --> 00:36:45,030
get the HTML that
represents that web page,

734
00:36:45,030 --> 00:36:47,190
the browser could
certainly poke around there

735
00:36:47,190 --> 00:36:49,380
before you even have a
chance to click on anything.

736
00:36:49,380 --> 00:36:53,530
And it could scrub or sanitize
these kinds of tracking parameters.

737
00:36:53,530 --> 00:36:57,240
Now, to be fair, if the browser
manufacturer doesn't necessarily

738
00:36:57,240 --> 00:37:00,090
know what the tracking
parameter is called

739
00:37:00,090 --> 00:37:03,030
or if maybe the website is
constantly changing the name

740
00:37:03,030 --> 00:37:07,390
or trying to mix things up,
this might not work so well.

741
00:37:07,390 --> 00:37:09,360
But it's at least an
attempt to try to put

742
00:37:09,360 --> 00:37:13,410
downward pressure on this very
commonplace technique of keeping

743
00:37:13,410 --> 00:37:14,820
track of you and me.

744
00:37:14,820 --> 00:37:17,610
Now, why is this parameter
able to track us?

745
00:37:17,610 --> 00:37:21,550
Well, this, too, can end up in those
server logs because this would be,

746
00:37:21,550 --> 00:37:24,045
for instance, the web
page that I am requesting,

747
00:37:24,045 --> 00:37:29,700
/ad_engagement?click_id= dot, dot,
dot, that could very well be logged

748
00:37:29,700 --> 00:37:31,830
by the server, stored
in a database, even.

749
00:37:31,830 --> 00:37:33,750
And they could use that
information to know

750
00:37:33,750 --> 00:37:37,290
exactly which pages I have clicked
on, because I visited those links,

751
00:37:37,290 --> 00:37:38,990
and even what ads I have seen.

752
00:37:38,990 --> 00:37:40,740
And maybe that's a
good thing commercially

753
00:37:40,740 --> 00:37:43,590
because now they know what
types of ads I'm clicking on.

754
00:37:43,590 --> 00:37:45,810
Now they can serve even
more of them to me.

755
00:37:45,810 --> 00:37:48,490
And that might be great for
them, but probably not so great,

756
00:37:48,490 --> 00:37:51,990
if not, annoying or
invasive for me and you.

757
00:37:51,990 --> 00:37:54,810
So something else to keep an eye
out for and something else that

758
00:37:54,810 --> 00:37:57,540
might guide your decision
making in the days and the years

759
00:37:57,540 --> 00:38:00,060
to come when it comes
to picking your browser.

760
00:38:00,060 --> 00:38:03,930
You don't necessarily have to nowadays
use the one that comes with your phone,

761
00:38:03,930 --> 00:38:05,670
comes with your laptop or desktop.

762
00:38:05,670 --> 00:38:08,190
You can, if more comfortable,
install something else.

763
00:38:08,190 --> 00:38:12,930
And increasingly, you and I are
having more and more options.

764
00:38:12,930 --> 00:38:17,550
Questions now on these
tracking parameters or anything

765
00:38:17,550 --> 00:38:20,010
prior with respect to our privacy?

766
00:38:20,010 --> 00:38:23,190
AUDIENCE: Are the cookies
the ones that track or are

767
00:38:23,190 --> 00:38:25,020
the ones that are being tracked?

768
00:38:25,020 --> 00:38:29,160
DAVID J. MALAN: The cookies are values
that are being used to track you.

769
00:38:29,160 --> 00:38:33,930
So recall that-- a metaphor for the
cookies is like that virtual handstamp.

770
00:38:33,930 --> 00:38:38,820
And so if all of these web servers are
putting ink on your hand and on my hand

771
00:38:38,820 --> 00:38:41,640
and because of HTTP,
you and I, our browsers

772
00:38:41,640 --> 00:38:44,010
are in the habit of
presenting these cookies,

773
00:38:44,010 --> 00:38:46,410
these handstamps to
every website we visit,

774
00:38:46,410 --> 00:38:49,680
that value is being used to track us.

775
00:38:49,680 --> 00:38:52,990
So cookies in and of themselves
are just a technology.

776
00:38:52,990 --> 00:38:57,130
It's a very simple idea storing a big
random value on your computer and mine

777
00:38:57,130 --> 00:38:58,750
just to uniquely identify us.

778
00:38:58,750 --> 00:39:02,590
They are necessary to give us
features like logging into websites,

779
00:39:02,590 --> 00:39:04,060
maintaining shopping carts.

780
00:39:04,060 --> 00:39:06,910
But very quickly, especially
since the internet from the get go

781
00:39:06,910 --> 00:39:09,430
has been largely free to use--

782
00:39:09,430 --> 00:39:11,710
or rather, a lot of
the internet has been

783
00:39:11,710 --> 00:39:14,620
free to use once you have
a connection, at least--

784
00:39:14,620 --> 00:39:17,950
they've been used, or
in some views, abused

785
00:39:17,950 --> 00:39:22,070
by the advertisers, the Facebooks,
and the others of the world.

786
00:39:22,070 --> 00:39:24,490
So another way to think
about tracking cookies

787
00:39:24,490 --> 00:39:27,430
is to consider them to be
third-party cookies because, indeed,

788
00:39:27,430 --> 00:39:29,920
even in the Google example,
that's how they're being used.

789
00:39:29,920 --> 00:39:34,750
If a website like example.com
is embedding Google Analytics,

790
00:39:34,750 --> 00:39:39,340
and therefore, some kind of HTML tag
that mentions google.com, well then,

791
00:39:39,340 --> 00:39:42,940
example.com is the first-party
in that story, so to speak.

792
00:39:42,940 --> 00:39:46,270
And google.com is the
third party in that story.

793
00:39:46,270 --> 00:39:48,700
What that means is that your
browser might get cookies

794
00:39:48,700 --> 00:39:51,400
from both example.com and google.com.

795
00:39:51,400 --> 00:39:54,890
But the most important ones,
presumably, are the first-party ones

796
00:39:54,890 --> 00:39:58,430
from example.com because that is
the website you chose to go to

797
00:39:58,430 --> 00:40:00,650
and whose functionality you want to use.

798
00:40:00,650 --> 00:40:03,950
The third-party functionality,
like tracking your clicks

799
00:40:03,950 --> 00:40:07,940
and your internet behavior on that
site via Google, that's third party.

800
00:40:07,940 --> 00:40:10,340
And so very commonly
do browsers nowadays

801
00:40:10,340 --> 00:40:15,230
certainly offer options via which
you can disable third-party cookies.

802
00:40:15,230 --> 00:40:17,240
And that tends to be
good for privacy sake

803
00:40:17,240 --> 00:40:20,480
because it means you're blocking
third parties like Google

804
00:40:20,480 --> 00:40:22,700
from keeping track of you via cookies.

805
00:40:22,700 --> 00:40:26,660
But, but, but that doesn't necessarily
mean the website isn't still

806
00:40:26,660 --> 00:40:29,210
using tracking parameters in some way.

807
00:40:29,210 --> 00:40:32,600
And you would only know that by actually
looking more closely at the URLs

808
00:40:32,600 --> 00:40:35,520
you're clicking on or that are
embedded in the web page itself.

809
00:40:35,520 --> 00:40:38,360
And that's where now browsers
and third-party software

810
00:40:38,360 --> 00:40:42,860
are additionally helping by helping us
remove not only those cookies, but even

811
00:40:42,860 --> 00:40:43,850
those parameters.

812
00:40:43,850 --> 00:40:45,920
But let's consider a
more concrete scenario

813
00:40:45,920 --> 00:40:50,540
of what third-party cookies are
and why they allow companies

814
00:40:50,540 --> 00:40:53,510
not only like Google to track
your behavior on one website,

815
00:40:53,510 --> 00:40:56,930
but even companies like
Google or other advertisers

816
00:40:56,930 --> 00:40:59,840
to track your behavior
on multiple websites.

817
00:40:59,840 --> 00:41:03,440
And in this sense, third
parties have increasingly

818
00:41:03,440 --> 00:41:08,840
been more powerful, more omniscient, for
instance, than the first-party websites

819
00:41:08,840 --> 00:41:10,700
that you and I are actually visiting.

820
00:41:10,700 --> 00:41:11,270
Why?

821
00:41:11,270 --> 00:41:13,520
Well, if there's a lot
of popular third parties

822
00:41:13,520 --> 00:41:17,390
out there, Google being one of them
for advertisements and for analytics,

823
00:41:17,390 --> 00:41:20,390
well, if lots of different
websites are using them--

824
00:41:20,390 --> 00:41:21,590
maybe Harvard's using them.

825
00:41:21,590 --> 00:41:22,400
Yale's using them.

826
00:41:22,400 --> 00:41:25,880
Stanford's using them-- then
that third party very quickly

827
00:41:25,880 --> 00:41:30,530
becomes more powerful than even any
of those individual parties alone.

828
00:41:30,530 --> 00:41:31,100
Why?

829
00:41:31,100 --> 00:41:36,830
Because that third party, if it is
being embedded at Harvard, Yale,

830
00:41:36,830 --> 00:41:39,560
and Stanford, that third
party Google, for instance,

831
00:41:39,560 --> 00:41:42,600
kind of has eyes into
all three websites.

832
00:41:42,600 --> 00:41:46,340
And if it sends the same cookie
to you on all three websites,

833
00:41:46,340 --> 00:41:49,670
Google might actually know that you're
poking around Harvard's, and Yale's

834
00:41:49,670 --> 00:41:52,940
and Stanford's website when
Harvard might have no idea you're

835
00:41:52,940 --> 00:41:54,380
checking out Yale and Stanford.

836
00:41:54,380 --> 00:41:57,890
And Stanford might have no idea
you're checking out Yale and Harvard.

837
00:41:57,890 --> 00:41:59,660
So what does this mean concretely?

838
00:41:59,660 --> 00:42:03,837
Well, consider some HTML here,
such as we've seen before.

839
00:42:03,837 --> 00:42:06,170
And I've highlighted a couple
of salient characteristics

840
00:42:06,170 --> 00:42:07,610
in this particular example.

841
00:42:07,610 --> 00:42:11,030
Notice that I've given in this web
page not only a body, which contains

842
00:42:11,030 --> 00:42:13,140
the body, the bulk of the web page.

843
00:42:13,140 --> 00:42:16,190
I've also included a head for
the web page, inside of which

844
00:42:16,190 --> 00:42:17,810
is another tag called Title.

845
00:42:17,810 --> 00:42:20,300
And I'm doing this just
to, one, demonstrate

846
00:42:20,300 --> 00:42:23,000
there are more tags than we have
seen in this language thus far.

847
00:42:23,000 --> 00:42:29,300
And specifically, this I claim is meant
to represent harvard.edu's own website,

848
00:42:29,300 --> 00:42:31,790
the title of which would
be Harvard, like in the tab

849
00:42:31,790 --> 00:42:33,050
along the top of the screen.

850
00:42:33,050 --> 00:42:37,140
And inside of the body of
this page for simplicity,

851
00:42:37,140 --> 00:42:40,010
let's assume that for now, there's
just one big advertisement.

852
00:42:40,010 --> 00:42:42,350
There's no content for
the sake of discussion.

853
00:42:42,350 --> 00:42:44,180
There's just one advertisement.

854
00:42:44,180 --> 00:42:46,620
Well, where is that
advertisement coming from?

855
00:42:46,620 --> 00:42:50,570
It's coming from, in this case,
example.com, or our friends at Google,

856
00:42:50,570 --> 00:42:53,600
specifically, a file called ad.gif.

857
00:42:53,600 --> 00:42:58,700
And this particular URL is being
used as the value of the source

858
00:42:58,700 --> 00:43:00,800
attribute of an image tag.

859
00:43:00,800 --> 00:43:02,100
So what do I mean by this?

860
00:43:02,100 --> 00:43:05,420
Well, if you visit harvard.edu
in the story, what you are seeing

861
00:43:05,420 --> 00:43:07,940
is a big advertisement,
a big GIF, a graphic

862
00:43:07,940 --> 00:43:11,840
that is coming from example.com.

863
00:43:11,840 --> 00:43:14,430
Now, what is the implication of that?

864
00:43:14,430 --> 00:43:17,130
Well, suppose that Yale
is doing the same thing.

865
00:43:17,130 --> 00:43:20,270
So here now, for the sake of
discussion, is the exact same HTML,

866
00:43:20,270 --> 00:43:22,100
except it lives at yale.edu.

867
00:43:22,100 --> 00:43:24,842
So the title of the page
has now changed to Yale.

868
00:43:24,842 --> 00:43:27,050
And moreover, just to make
things really interesting,

869
00:43:27,050 --> 00:43:28,610
let's add Stanford to the mix.

870
00:43:28,610 --> 00:43:30,240
Same exact page.

871
00:43:30,240 --> 00:43:35,630
So the point of this story is that
Harvard, and Yale, and Stanford are all

872
00:43:35,630 --> 00:43:39,590
using the same third party,
example.com in this case

873
00:43:39,590 --> 00:43:42,500
or maybe someone like
Google in the real world.

874
00:43:42,500 --> 00:43:45,050
And they're requesting
moreover the same GIF.

875
00:43:45,050 --> 00:43:47,030
And so the same file is being accessed.

876
00:43:47,030 --> 00:43:49,370
But that even alone isn't
a strict requirement.

877
00:43:49,370 --> 00:43:53,620
The same website is being accessed
by all three of these first parties.

878
00:43:53,620 --> 00:43:54,810
So what does that mean?

879
00:43:54,810 --> 00:43:59,010
Suppose that you open up your browser
and you first visit harvard.edu,

880
00:43:59,010 --> 00:44:02,940
your browser is going to download
the HTML for Harvard's website.

881
00:44:02,940 --> 00:44:05,580
It's going to see that, oh,
there's an image tag in there.

882
00:44:05,580 --> 00:44:09,900
And that image tag wants to show
this ad.gif from example.com.

883
00:44:09,900 --> 00:44:12,210
So your browser is
automatically, by nature

884
00:44:12,210 --> 00:44:14,520
of how browsers work,
going to send a second HTTP

885
00:44:14,520 --> 00:44:20,280
request, this time requesting
ad.gif from the host, example.com.

886
00:44:20,280 --> 00:44:22,710
And just to tie today's
stories together,

887
00:44:22,710 --> 00:44:29,010
it's going to include, probably,
a referrer, HTTP header that

888
00:44:29,010 --> 00:44:30,855
specifies where I'm coming from.

889
00:44:30,855 --> 00:44:32,730
And that's useful for
our purposes because it

890
00:44:32,730 --> 00:44:34,770
puts these requests into context.

891
00:44:34,770 --> 00:44:40,110
Now that server, example.com, or
Google, in the case of the real world,

892
00:44:40,110 --> 00:44:45,090
is going to probably respond with 200
OK like, OK, here is the advertisement.

893
00:44:45,090 --> 00:44:48,450
And it's going to include not
only the image, but also an HTTP

894
00:44:48,450 --> 00:44:49,450
header of its own.

895
00:44:49,450 --> 00:44:51,810
And this is our old
friend set-cookie, where

896
00:44:51,810 --> 00:44:53,740
in this case, for the
sake of discussion,

897
00:44:53,740 --> 00:44:57,460
I'm going to propose that it's setting
a cookie on my computer called ID

898
00:44:57,460 --> 00:45:00,700
because this is going to be my
unique identifier for example.com.

899
00:45:00,700 --> 00:45:04,930
Its value is going to be the one I keep
using for discussion's sake, 1234abcd.

900
00:45:04,930 --> 00:45:07,450
But that would be some big
random value for each of us.

901
00:45:07,450 --> 00:45:08,260
And my gosh.

902
00:45:08,260 --> 00:45:09,790
This thing is going to last a year.

903
00:45:09,790 --> 00:45:13,340
That's the number of
seconds in 365 days.

904
00:45:13,340 --> 00:45:16,180
So this cookie is being
planted on my computer

905
00:45:16,180 --> 00:45:21,130
by example.com because
I visited harvard.edu.

906
00:45:21,130 --> 00:45:22,930
So Harvard is the first party.

907
00:45:22,930 --> 00:45:26,480
Example.com is the third
party in this case.

908
00:45:26,480 --> 00:45:28,570
But here now is the concern.

909
00:45:28,570 --> 00:45:32,590
When I visit yale.edu
with that same browser,

910
00:45:32,590 --> 00:45:36,100
my hand has been stamped
by example.com already.

911
00:45:36,100 --> 00:45:40,090
And so what happens is that
my browser now presents

912
00:45:40,090 --> 00:45:44,920
that handstamp to example.com, sending
the same ID and the same value,

913
00:45:44,920 --> 00:45:46,360
that is, the same handstamp.

914
00:45:46,360 --> 00:45:48,850
The host is as before example.com.

915
00:45:48,850 --> 00:45:51,740
But this time, the referrer
happens to be Yale.

916
00:45:51,740 --> 00:45:55,120
So in other words, after I
visited Harvard and my hand

917
00:45:55,120 --> 00:45:58,960
has been stamped with this tracking
cookie, this third-party cookie

918
00:45:58,960 --> 00:46:02,290
from example.com, my browser,
when I visit yale.edu,

919
00:46:02,290 --> 00:46:05,830
is going to present that same
handstamp again, this time,

920
00:46:05,830 --> 00:46:08,320
to example.com with this referrer.

921
00:46:08,320 --> 00:46:11,170
The next time I use my
browser to visit stanford.edu,

922
00:46:11,170 --> 00:46:13,630
the same message is going
to be sent from my browser

923
00:46:13,630 --> 00:46:18,190
to example.com to request
that same ad, this time now

924
00:46:18,190 --> 00:46:20,740
from stanford.edu's website.

925
00:46:20,740 --> 00:46:22,360
Now, what's the implication?

926
00:46:22,360 --> 00:46:26,710
Via these three HTTP
requests, example.com

927
00:46:26,710 --> 00:46:30,160
knows that I'm visiting
Stanford, and before that, Yale

928
00:46:30,160 --> 00:46:32,110
and before that, Harvard.

929
00:46:32,110 --> 00:46:34,990
And none of Harvard,
or Yale, or Stanford

930
00:46:34,990 --> 00:46:37,630
necessarily know that I'm visiting
any of those other websites.

931
00:46:37,630 --> 00:46:39,950
The third party is the more powerful.

932
00:46:39,950 --> 00:46:44,140
It's the more all seeing, simply because
example.com, or in the real world,

933
00:46:44,140 --> 00:46:46,570
Google, is just so
darn popular, that it's

934
00:46:46,570 --> 00:46:51,520
embedded in so many darn websites,
Google and others almost everything,

935
00:46:51,520 --> 00:46:54,040
dare say, about what you
and I are doing on the web

936
00:46:54,040 --> 00:46:57,710
because these ads are all
over the place in this way.

937
00:46:57,710 --> 00:46:59,770
So we've seen a very simple example.

938
00:46:59,770 --> 00:47:04,720
But it's simple because cookies
and HTTP really are relatively.

939
00:47:04,720 --> 00:47:07,030
It's once you realize
how they work, that you

940
00:47:07,030 --> 00:47:09,460
can use them not only to solve
compelling problems for all

941
00:47:09,460 --> 00:47:13,250
of us, sessions, and
shopping carts, and the like,

942
00:47:13,250 --> 00:47:16,090
but also can be used to
monetize the internet

943
00:47:16,090 --> 00:47:19,750
and has been used historically to
monetize the internet, or even worse,

944
00:47:19,750 --> 00:47:24,710
perhaps, for us, to track our
individual clicks and behavior.

945
00:47:24,710 --> 00:47:27,610
So let me pause here and see
if there's any questions now

946
00:47:27,610 --> 00:47:31,060
on third-party cookies
and why, therefore, it's

947
00:47:31,060 --> 00:47:35,140
perhaps so compelling for you or
me to opt in to disabling them,

948
00:47:35,140 --> 00:47:40,030
or better yet, to use browsers that
are starting to block them for us.

949
00:47:40,030 --> 00:47:43,120
AUDIENCE: What browsers are
more secure among others

950
00:47:43,120 --> 00:47:45,035
considering tracking parameters?

951
00:47:45,035 --> 00:47:45,910
DAVID J. MALAN: Sure.

952
00:47:45,910 --> 00:47:46,510
A quick tweak.

953
00:47:46,510 --> 00:47:48,260
I wouldn't say that
some browsers are more

954
00:47:48,260 --> 00:47:50,350
secure than others in this context.

955
00:47:50,350 --> 00:47:53,620
I would say that want browsers
that are more privacy conscious

956
00:47:53,620 --> 00:47:56,830
or privacy preserving because that's
what we're talking about today.

957
00:47:56,830 --> 00:47:59,080
Hopefully, all of them
are just as secure when

958
00:47:59,080 --> 00:48:03,820
it comes to HTTPS and the encryption
that's just keeping our data protected

959
00:48:03,820 --> 00:48:05,830
between points A and B.

960
00:48:05,830 --> 00:48:10,930
So generally, Safari has been pretty
good when it comes to privacy.

961
00:48:10,930 --> 00:48:15,035
And they are the ones that very
recently that you're using now

962
00:48:15,035 --> 00:48:18,160
announced that they're going to start
giving people the feature of removing

963
00:48:18,160 --> 00:48:20,380
tracking parameters from URLs.

964
00:48:20,380 --> 00:48:22,510
In fact, the sample
URL I gave was actually

965
00:48:22,510 --> 00:48:25,990
from Apple's recent
announcement about exactly that.

966
00:48:25,990 --> 00:48:29,920
DuckDuckGo is probably the most
popular third-party browser

967
00:48:29,920 --> 00:48:32,440
that is very privacy
conscious and tries to disable

968
00:48:32,440 --> 00:48:34,490
a lot of these tracking behaviors.

969
00:48:34,490 --> 00:48:36,580
Another one is Brave.

970
00:48:36,580 --> 00:48:39,820
Perhaps, the worst offender
is probably Chrome,

971
00:48:39,820 --> 00:48:43,120
even though I, myself, am guilty
of using it myself because it's

972
00:48:43,120 --> 00:48:45,190
so integrated into Google's ecosystem.

973
00:48:45,190 --> 00:48:47,140
But Google, of course,
has made their business

974
00:48:47,140 --> 00:48:50,030
on monetizing your behavior and mine.

975
00:48:50,030 --> 00:48:54,000
So that is, perhaps, one to put
toward the bottom of the list

976
00:48:54,000 --> 00:48:55,630
if you're concerned about this.

977
00:48:55,630 --> 00:48:57,380
So that's kind of how
I would rank things.

978
00:48:57,380 --> 00:48:58,280
And there's yet others.

979
00:48:58,280 --> 00:48:59,870
But I think those are
some of the most popular.

980
00:48:59,870 --> 00:49:01,970
And then, of course, in
the Microsoft ecosystem,

981
00:49:01,970 --> 00:49:04,780
there is Edge and Firefox too.

982
00:49:04,780 --> 00:49:06,530
I should have put them
higher on the list.

983
00:49:06,530 --> 00:49:09,650
They are more privacy conscious,
I do believe, than Google.

984
00:49:09,650 --> 00:49:12,690
So with all of these mechanisms
for tracking in mind,

985
00:49:12,690 --> 00:49:15,350
what can we do to protect
all the more of our privacy?

986
00:49:15,350 --> 00:49:18,350
Well, you might already know of
this feature, private browsing.

987
00:49:18,350 --> 00:49:22,220
So you don't necessarily have to
delete all of your browser history

988
00:49:22,220 --> 00:49:23,850
and delete all of your cookies.

989
00:49:23,850 --> 00:49:26,122
You can instead, on occasion,
open up a special type

990
00:49:26,122 --> 00:49:27,830
of window, which most
of today's browsers

991
00:49:27,830 --> 00:49:31,040
support that puts you into
private mode or incognito mode.

992
00:49:31,040 --> 00:49:34,460
And you can think of this as giving
you just a different chunk of memory

993
00:49:34,460 --> 00:49:38,360
in the computer that doesn't know any of
your past browser history, that doesn't

994
00:49:38,360 --> 00:49:41,210
have any of your past cookies,
that doesn't remember any

995
00:49:41,210 --> 00:49:42,920
of your past usernames and passwords.

996
00:49:42,920 --> 00:49:47,150
You're sort of starting fresh, so
that everything you do in that window

997
00:49:47,150 --> 00:49:48,110
is brand new.

998
00:49:48,110 --> 00:49:50,180
The catch, though, is
that everything you do in

999
00:49:50,180 --> 00:49:56,270
that window still works exactly as the
web works as we have been describing.

1000
00:49:56,270 --> 00:49:58,670
So you're still might
have tracking parameters.

1001
00:49:58,670 --> 00:50:00,800
You still might have tracking cookies.

1002
00:50:00,800 --> 00:50:02,840
You still might have server logs.

1003
00:50:02,840 --> 00:50:07,740
But when you close that private window
or you close that incognito mode,

1004
00:50:07,740 --> 00:50:11,580
at least, the information is
discarded from your computer,

1005
00:50:11,580 --> 00:50:13,790
so that if tomorrow, you
do the exact same thing

1006
00:50:13,790 --> 00:50:16,790
and open up an incognito
window again, then

1007
00:50:16,790 --> 00:50:19,670
it's as though you're starting
fresh with that server,

1008
00:50:19,670 --> 00:50:23,030
except for the reality, as
per our past discussion,

1009
00:50:23,030 --> 00:50:26,150
that fingerprinting is
still a possibility.

1010
00:50:26,150 --> 00:50:29,840
Your IP address can still be factored
in as can be other information

1011
00:50:29,840 --> 00:50:31,610
that your browser
might still be leaking.

1012
00:50:31,610 --> 00:50:34,610
But what you're not doing is
contaminating, so to speak,

1013
00:50:34,610 --> 00:50:37,310
your general browsing
history with specifically

1014
00:50:37,310 --> 00:50:39,650
what you're using that window for.

1015
00:50:39,650 --> 00:50:43,040
What you should realize, too, that
private browsing or incognito mode

1016
00:50:43,040 --> 00:50:44,850
is entirely client side.

1017
00:50:44,850 --> 00:50:47,300
So particularly, those
logs that we have mentioned

1018
00:50:47,300 --> 00:50:49,460
are still being stored by the server.

1019
00:50:49,460 --> 00:50:52,910
They might be storing, perhaps, a
different tracking cookie or parameter

1020
00:50:52,910 --> 00:50:56,390
for you because it doesn't
necessarily recognize you when

1021
00:50:56,390 --> 00:50:58,340
you're in private or incognito mode.

1022
00:50:58,340 --> 00:51:02,240
But it doesn't mean that your tracks
are completely absent from the internet.

1023
00:51:02,240 --> 00:51:05,420
Rather, it's really just scrubbing
them from your local computer

1024
00:51:05,420 --> 00:51:09,440
and decreasing the probability,
but not eliminating the probability

1025
00:51:09,440 --> 00:51:12,125
that a server still knows that it's you.

1026
00:51:12,125 --> 00:51:14,160
So I would use with care.

1027
00:51:14,160 --> 00:51:17,240
But with that said, if you take
a course in web development

1028
00:51:17,240 --> 00:51:21,320
or you already design your own websites,
using private browsing or incognito

1029
00:51:21,320 --> 00:51:23,732
mode can also be useful
for development purposes

1030
00:51:23,732 --> 00:51:25,940
because it's a way of opening
a brand new window that

1031
00:51:25,940 --> 00:51:28,790
has no recollection of
maybe past bugs that you had

1032
00:51:28,790 --> 00:51:30,740
or past web pages that you clicked on.

1033
00:51:30,740 --> 00:51:33,860
And it's very commonly used
as part of development tools

1034
00:51:33,860 --> 00:51:40,140
to actually facilitate and mimic the
idea of starting fresh with some site.

1035
00:51:40,140 --> 00:51:43,050
Super cookies, though,
these sound delicious,

1036
00:51:43,050 --> 00:51:46,870
but these two are kind of the worst of
cookies that we've discussed already.

1037
00:51:46,870 --> 00:51:49,110
We saw session cookies
for maintaining state.

1038
00:51:49,110 --> 00:51:51,900
We saw tracking cookies
for tracking you.

1039
00:51:51,900 --> 00:51:54,780
Super cookies are not so super, really.

1040
00:51:54,780 --> 00:51:57,660
These are cookies that
are typically injected

1041
00:51:57,660 --> 00:52:01,440
by a third party, like your
company, your university,

1042
00:52:01,440 --> 00:52:06,570
or your internet service provider
into your HTTP request, which

1043
00:52:06,570 --> 00:52:10,110
is to say, if you, from your
browser, visit some website,

1044
00:52:10,110 --> 00:52:13,620
that traffic, of course, goes
from your laptop or phone

1045
00:52:13,620 --> 00:52:17,670
through some internet service provider,
whether it's on campus, or home,

1046
00:52:17,670 --> 00:52:19,660
or wirelessly in the real world.

1047
00:52:19,660 --> 00:52:22,830
And if whoever is providing
you with that internet service

1048
00:52:22,830 --> 00:52:26,430
can see the contents of
that virtual envelope,

1049
00:52:26,430 --> 00:52:28,290
there's technically
nothing stopping them

1050
00:52:28,290 --> 00:52:30,540
from opening up the
envelope, so to speak,

1051
00:52:30,540 --> 00:52:34,060
and adding one or more
HTTP headers of their own.

1052
00:52:34,060 --> 00:52:36,780
And so mobile phone carriers,
for instance, in the past

1053
00:52:36,780 --> 00:52:39,300
have been known to do this,
whereby, if you are just

1054
00:52:39,300 --> 00:52:43,390
requesting a website, like
example.com from your phone,

1055
00:52:43,390 --> 00:52:47,800
they might-- halfway
between you and that server,

1056
00:52:47,800 --> 00:52:50,410
they might inject a cookie of their own.

1057
00:52:50,410 --> 00:52:53,800
For the sake of discussion, I'm going to
use the same name and value as before.

1058
00:52:53,800 --> 00:52:56,710
id=1234abcd.

1059
00:52:56,710 --> 00:53:00,760
But what's noteworthy here is that that
value is not coming from your phone.

1060
00:53:00,760 --> 00:53:02,740
It is not coming from your browser.

1061
00:53:02,740 --> 00:53:04,473
You can clear all of your cookies.

1062
00:53:04,473 --> 00:53:05,890
You can clear all of your history.

1063
00:53:05,890 --> 00:53:08,600
You can use incognito or
private mode on your phone.

1064
00:53:08,600 --> 00:53:11,290
You're not going to see any
trace of that client side

1065
00:53:11,290 --> 00:53:16,750
because the darn thing is being
injected into your traffic between you,

1066
00:53:16,750 --> 00:53:19,180
point A, and the server, point B.

1067
00:53:19,180 --> 00:53:22,900
So this is sort of a canonical example
of a machine in the middle attack.

1068
00:53:22,900 --> 00:53:26,080
But your internet service provider
in this telling of the story

1069
00:53:26,080 --> 00:53:28,900
is doing it because
they want to track you.

1070
00:53:28,900 --> 00:53:31,810
Or they want-- because of
advertising relationships

1071
00:53:31,810 --> 00:53:33,790
they might have with
some websites, they want

1072
00:53:33,790 --> 00:53:37,070
to make sure that you can
be tracked by that website,

1073
00:53:37,070 --> 00:53:40,390
even if you have opted out or
have been clearing proactively

1074
00:53:40,390 --> 00:53:41,770
your very own cookies.

1075
00:53:41,770 --> 00:53:45,040
So suffice it to say, these have
been particularly controversial.

1076
00:53:45,040 --> 00:53:48,310
And thankfully, you and I do
have a pretty good defense here.

1077
00:53:48,310 --> 00:53:51,790
Just never use HTTP without encryption.

1078
00:53:51,790 --> 00:53:58,450
If URLs are always https:// and
then something, theoretically,

1079
00:53:58,450 --> 00:54:02,620
this attack or this "feature" of your
mobile phone carrier should not be

1080
00:54:02,620 --> 00:54:03,140
possible.

1081
00:54:03,140 --> 00:54:03,640
Why?

1082
00:54:03,640 --> 00:54:06,130
Because if the contents of
the envelope are encrypted,

1083
00:54:06,130 --> 00:54:08,560
not only can't they see
what's actually inside,

1084
00:54:08,560 --> 00:54:12,040
they can't add anything to the mix
because they don't have the key that's

1085
00:54:12,040 --> 00:54:14,530
being used to encrypt that information.

1086
00:54:14,530 --> 00:54:19,243
So simply using always HTTPS is
one solution to this problem.

1087
00:54:19,243 --> 00:54:21,910
And also, at least, in the US,
some of the mobile phone carriers

1088
00:54:21,910 --> 00:54:23,500
got a lot of backlash for this.

1089
00:54:23,500 --> 00:54:28,870
But so, you can occasionally log into
your cell phone provider's website,

1090
00:54:28,870 --> 00:54:33,410
go through a bunch of menus, find an
option to opt out of this feature.

1091
00:54:33,410 --> 00:54:37,240
But I will say from experience, that
they typically bury these options too.

1092
00:54:37,240 --> 00:54:40,120
And so it's not necessarily
even the iciest thing to find.

1093
00:54:40,120 --> 00:54:45,070
But again, this is just a natural
result of the underlying technology

1094
00:54:45,070 --> 00:54:51,000
that we're being used, or if you prefer,
abused, for alternative purposes.

1095
00:54:51,000 --> 00:54:51,500
All right.

1096
00:54:51,500 --> 00:54:54,310
Let me pause here and see
if there's any questions now

1097
00:54:54,310 --> 00:54:59,380
on these super cookies, which indeed,
are not so super or anything prior.

1098
00:54:59,380 --> 00:55:02,560
AUDIENCE: Given that cookies
store passwords and emails,

1099
00:55:02,560 --> 00:55:07,540
can the adversary impersonate
another person by copying that cookie

1100
00:55:07,540 --> 00:55:13,237
and pasting it into his own
computer and visiting that website?

1101
00:55:13,237 --> 00:55:14,570
DAVID J. MALAN: A good question.

1102
00:55:14,570 --> 00:55:19,990
So cookies can be used to store user
names, email addresses, even passwords,

1103
00:55:19,990 --> 00:55:22,270
though, I would generally
not recommend doing this.

1104
00:55:22,270 --> 00:55:24,882
But they theoretically
should be secure, even

1105
00:55:24,882 --> 00:55:26,590
if you're storing
those values in cookies

1106
00:55:26,590 --> 00:55:30,370
because they're going back and forth
between the browser and the server

1107
00:55:30,370 --> 00:55:34,120
using encryption if
HTTPS is, indeed, in use.

1108
00:55:34,120 --> 00:55:37,480
A danger, though, is that if someone
has physical access to your computer,

1109
00:55:37,480 --> 00:55:40,660
it's very easy to poke around your
own browser's cookies, at which point,

1110
00:55:40,660 --> 00:55:44,180
they're going to see your password,
which is probably not a good thing.

1111
00:55:44,180 --> 00:55:46,750
So on an alternative
would be, for instance,

1112
00:55:46,750 --> 00:55:50,350
for a browser to encrypt the cookie
or minimally digitally sign it,

1113
00:55:50,350 --> 00:55:54,310
so that it can be identified as
belonging to that same server.

1114
00:55:54,310 --> 00:55:58,360
But even better, I dare
say, would be for servers

1115
00:55:58,360 --> 00:56:03,160
to only plant big random values
as cookies on your computer,

1116
00:56:03,160 --> 00:56:06,760
like this virtual
handstamp, and then store

1117
00:56:06,760 --> 00:56:11,020
recollection of your username,
email, and/or password on the server.

1118
00:56:11,020 --> 00:56:15,190
So stamp my hand to remember
who I am and that I'm logged in,

1119
00:56:15,190 --> 00:56:19,910
but don't bother expecting my browser
to send my username, my email address,

1120
00:56:19,910 --> 00:56:21,610
my password again and again.

1121
00:56:21,610 --> 00:56:24,280
It should suffice to
send that just once.

1122
00:56:24,280 --> 00:56:25,555
Other questions here?

1123
00:56:25,555 --> 00:56:28,040
AUDIENCE: I've heard
that it's possible--

1124
00:56:28,040 --> 00:56:30,400
for example, if I'm
writing a text to someone,

1125
00:56:30,400 --> 00:56:35,270
it's possible to intercept, to alter
my text and send it on my behalf.

1126
00:56:35,270 --> 00:56:40,020
So it's going to be a different
message, so it's possible to ask, maybe,

1127
00:56:40,020 --> 00:56:41,710
for sensitive information.

1128
00:56:41,710 --> 00:56:45,840
So I was wondering, don't those
messengers use something like cookies?

1129
00:56:45,840 --> 00:56:46,917
How can this be possible?

1130
00:56:46,917 --> 00:56:48,250
DAVID J. MALAN: A good question.

1131
00:56:48,250 --> 00:56:52,410
So SMS, or traditional
texting, is generally insecure.

1132
00:56:52,410 --> 00:56:56,080
It is very easy for someone
to forge your phone number.

1133
00:56:56,080 --> 00:56:58,710
And in fact, if you've gotten
a lot of spam via text,

1134
00:56:58,710 --> 00:57:01,020
that might be exactly what is happening.

1135
00:57:01,020 --> 00:57:07,050
Or worse, it's also possible, recall, to
steal your SIM card essentially or port

1136
00:57:07,050 --> 00:57:11,110
it to another carrier, so that someone
can intercept all of your actual texts.

1137
00:57:11,110 --> 00:57:14,340
So in general, nowadays, you
should be reducing, if not,

1138
00:57:14,340 --> 00:57:18,570
eliminating your usage of SMS, at least,
for anything important or anything

1139
00:57:18,570 --> 00:57:19,740
you want to keep private.

1140
00:57:19,740 --> 00:57:26,730
When it comes to other messaging tools,
like iMessage, like WhatsApp, Signal,

1141
00:57:26,730 --> 00:57:31,020
Telegram, there's a lot of products
nowadays, third-party or otherwise,

1142
00:57:31,020 --> 00:57:33,580
that use end-to-end
encryption, which recall,

1143
00:57:33,580 --> 00:57:35,200
we discussed a couple of classes ago.

1144
00:57:35,200 --> 00:57:39,060
And in that case, even though the
data is going through a company like

1145
00:57:39,060 --> 00:57:42,940
Facebook, theoretically, assuming
they're behaving honorably and have

1146
00:57:42,940 --> 00:57:45,520
implemented end-to-end
encryption properly,

1147
00:57:45,520 --> 00:57:49,570
then even they cannot see the
message going between their servers.

1148
00:57:49,570 --> 00:57:51,190
And that is independent of cookies.

1149
00:57:51,190 --> 00:57:54,160
Cookies have no part of that solution.

1150
00:57:54,160 --> 00:57:58,210
That solution is entirely thanks
to cryptography and encryption

1151
00:57:58,210 --> 00:58:01,230
with digital signatures.

1152
00:58:01,230 --> 00:58:01,840
All right.

1153
00:58:01,840 --> 00:58:04,958
So let's consider one other
threat to your privacy

1154
00:58:04,958 --> 00:58:06,750
that you might not
necessarily have thought

1155
00:58:06,750 --> 00:58:10,740
about that isn't relate just to the web,
but really, your use of the internet

1156
00:58:10,740 --> 00:58:14,490
more generally, namely,
DNS, the Domain Name System.

1157
00:58:14,490 --> 00:58:18,510
Thankfully, even though computers on
the internet all have IP addresses,

1158
00:58:18,510 --> 00:58:21,510
these unique numeric addresses
that we've discussed,

1159
00:58:21,510 --> 00:58:25,350
you and I don't have to remember
what server's IP addresses are

1160
00:58:25,350 --> 00:58:28,830
because servers typically
have domain names, something

1161
00:58:28,830 --> 00:58:34,020
like harvard.edu, yale.edu,
stanford.edu, google.com, amazon.com,

1162
00:58:34,020 --> 00:58:35,160
and others.

1163
00:58:35,160 --> 00:58:39,600
But how then-- when you type in any of
those domain names into your browser

1164
00:58:39,600 --> 00:58:41,880
or into any piece of
software on the internet,

1165
00:58:41,880 --> 00:58:47,580
how does your browser or your computer
know what IP address to contact?

1166
00:58:47,580 --> 00:58:50,850
Well, it turns out that there's a
domain name system in the world.

1167
00:58:50,850 --> 00:58:53,220
And this is a system
deployed throughout the world

1168
00:58:53,220 --> 00:58:57,870
on the internet whose purpose in life
is to translate domain names to IP

1169
00:58:57,870 --> 00:59:00,640
addresses, so that on the
outside of those envelopes

1170
00:59:00,640 --> 00:59:04,760
can, indeed, go the IP addresses
of source and destination.

1171
00:59:04,760 --> 00:59:07,840
But you and I, as humans,
don't need to know or remember

1172
00:59:07,840 --> 00:59:09,890
exactly what those IP addresses are.

1173
00:59:09,890 --> 00:59:11,890
You can think about this
back in the day of when

1174
00:59:11,890 --> 00:59:13,848
we were in the habit of
typing in phone numbers

1175
00:59:13,848 --> 00:59:16,520
to actual analog landline telephones.

1176
00:59:16,520 --> 00:59:19,368
It was actually pretty hard to
remember lots of people's numbers.

1177
00:59:19,368 --> 00:59:21,160
And you might even have
had an address book

1178
00:59:21,160 --> 00:59:23,110
that you looked up people's numbers in.

1179
00:59:23,110 --> 00:59:24,640
Or there were certain mnemonics.

1180
00:59:24,640 --> 00:59:27,880
For instance, in the United States,
there was a number, 1-800-COLLECT,

1181
00:59:27,880 --> 00:59:33,370
C-O-L-L-E-C-T, which was just much
easier to remember than the actual

1182
00:59:33,370 --> 00:59:35,770
numbers for making a collect call.

1183
00:59:35,770 --> 00:59:38,560
The equivalent on the
internet is DNS, which

1184
00:59:38,560 --> 00:59:42,610
just automates this process for us,
so that every website, every service

1185
00:59:42,610 --> 00:59:46,480
can have its own unique name,
but it's translated automatically

1186
00:59:46,480 --> 00:59:52,030
for us via DNS servers throughout the
world to the corresponding IP address.

1187
00:59:52,030 --> 00:59:54,410
But why is this problematic?

1188
00:59:54,410 --> 00:59:58,970
Well, it turns out that DNS servers are
typically in a few different places.

1189
00:59:58,970 --> 01:00:03,520
One, you probably have one in your home,
or your company, or your university.

1190
01:00:03,520 --> 01:00:07,690
And it probably is built into, if
in your home, the router, the device

1191
01:00:07,690 --> 01:00:10,120
that you're using just to
connect to the internet.

1192
01:00:10,120 --> 01:00:14,290
But your internet service provider
also tends to have a DNS server.

1193
01:00:14,290 --> 01:00:16,750
And that DNS server
probably knows about way

1194
01:00:16,750 --> 01:00:20,950
more IP addresses than your
own home does because why would

1195
01:00:20,950 --> 01:00:24,030
your own home network know about all
of the IP addresses in the world?

1196
01:00:24,030 --> 01:00:26,530
But with that said, why would
your internet service provider

1197
01:00:26,530 --> 01:00:30,400
know about all of the possible
IP addresses and domain names

1198
01:00:30,400 --> 01:00:31,030
in the world?

1199
01:00:31,030 --> 01:00:32,830
Well, suffice it to
say for our purposes,

1200
01:00:32,830 --> 01:00:34,580
there's a hierarchical system.

1201
01:00:34,580 --> 01:00:36,910
So even if your home
router doesn't know,

1202
01:00:36,910 --> 01:00:39,370
even if your internet service
provider doesn't know,

1203
01:00:39,370 --> 01:00:42,580
there's some other server on
the internet that can eventually

1204
01:00:42,580 --> 01:00:46,870
give you the answer to a question
like, what is harvard.edu's IP address?

1205
01:00:46,870 --> 01:00:51,170
What is yale.edu's IP
address and so forth?

1206
01:00:51,170 --> 01:00:55,120
And for efficiency, once that answer
has been figured out somewhere,

1207
01:00:55,120 --> 01:00:59,620
then your internet service provider
might remember, or cache, the answer.

1208
01:00:59,620 --> 01:01:04,060
And even your home router, and heck,
even your device or your browser

1209
01:01:04,060 --> 01:01:06,580
might remember the same
answer for efficiency,

1210
01:01:06,580 --> 01:01:09,650
so we don't have to keep
asking the same question.

1211
01:01:09,650 --> 01:01:14,950
And it turns out by convention, DNS uses
port 53, if you recall our discussion,

1212
01:01:14,950 --> 01:01:21,610
of also using unique numbers to identify
things like HTTP, or 80, HTTPS, or 443,

1213
01:01:21,610 --> 01:01:23,830
or 22 for SSH.

1214
01:01:23,830 --> 01:01:26,170
DNS tends to use 53.

1215
01:01:26,170 --> 01:01:29,830
But the catch is that
the traffic used for DNS

1216
01:01:29,830 --> 01:01:35,080
is typically unencrypted, which means
that when your phone, or your laptop,

1217
01:01:35,080 --> 01:01:38,830
or your desktop is asking your home
device, or maybe your internet service

1218
01:01:38,830 --> 01:01:42,940
provider, or someone else, what
is the IP address for harvard.edu,

1219
01:01:42,940 --> 01:01:47,260
or yale.edu, or the like, you're
actually announcing to the world what

1220
01:01:47,260 --> 01:01:49,210
website you are about to visit.

1221
01:01:49,210 --> 01:01:49,750
Why?

1222
01:01:49,750 --> 01:01:52,150
Because you're waiting for
a response from the DNS

1223
01:01:52,150 --> 01:01:55,850
server to actually tell you
the corresponding IP address.

1224
01:01:55,850 --> 01:01:56,950
So this isn't great.

1225
01:01:56,950 --> 01:02:00,730
And moreover, your internet
service provider, therefore,

1226
01:02:00,730 --> 01:02:04,360
knows all of this information
about you because every time

1227
01:02:04,360 --> 01:02:07,570
you ask for a new website that you've
never been to before, your home

1228
01:02:07,570 --> 01:02:09,740
network probably doesn't
know the IP address,

1229
01:02:09,740 --> 01:02:12,275
so you have to ask your
internet service provider.

1230
01:02:12,275 --> 01:02:13,900
And again, they might ask someone else.

1231
01:02:13,900 --> 01:02:17,240
But the internet service provider
is going to know now that you asked.

1232
01:02:17,240 --> 01:02:20,470
So your internet service provider,
be it for your home network

1233
01:02:20,470 --> 01:02:23,320
or for your cellular
phone, pretty much knows

1234
01:02:23,320 --> 01:02:26,110
every website you've
ever been to, assuming

1235
01:02:26,110 --> 01:02:28,600
they're logging this information,
which they probably are,

1236
01:02:28,600 --> 01:02:32,320
unless there are regulatory or legal
requirements that say they can't or

1237
01:02:32,320 --> 01:02:34,400
they can't for very long.

1238
01:02:34,400 --> 01:02:37,340
Now, why is this the case?

1239
01:02:37,340 --> 01:02:40,690
Well, the domain name
system essentially requires

1240
01:02:40,690 --> 01:02:42,190
that we ask these very questions.

1241
01:02:42,190 --> 01:02:45,070
And if the internet service
providers remember these answers,

1242
01:02:45,070 --> 01:02:48,640
well, they can keep track of everywhere
we've been, at least, at a high level.

1243
01:02:48,640 --> 01:02:53,020
DNS only gives them back a translation
from the domain name to the IP address.

1244
01:02:53,020 --> 01:02:57,340
What it does not include is the
specific page that you're looking at,

1245
01:02:57,340 --> 01:03:01,257
the specific URL, the folder,
the file that you're looking at.

1246
01:03:01,257 --> 01:03:03,090
So your internet service
provider might know

1247
01:03:03,090 --> 01:03:05,880
you're visiting somewhere
on harvard.edu because you

1248
01:03:05,880 --> 01:03:07,440
asked, of course, for its IP address.

1249
01:03:07,440 --> 01:03:10,500
But they don't know what
department you were looking for

1250
01:03:10,500 --> 01:03:13,260
or what course you were
looking at or the like.

1251
01:03:13,260 --> 01:03:16,410
But there's still a decent amount of
invasion, therefore, of your privacy

1252
01:03:16,410 --> 01:03:21,120
if you'd rather that ISP or someone
else just not know that information.

1253
01:03:21,120 --> 01:03:25,170
So increasingly, there are
alternatives to the standard DNS

1254
01:03:25,170 --> 01:03:31,210
functionality, one of which is called
DNS over HTTPS, or DoH for short.

1255
01:03:31,210 --> 01:03:32,850
This means exactly that.

1256
01:03:32,850 --> 01:03:37,230
Instead of just sending out DNS
requests unencrypted on port 53

1257
01:03:37,230 --> 01:03:41,520
to the local DNS server, now they're
sent, potentially if you enable this,

1258
01:03:41,520 --> 01:03:43,470
over HTTPS.

1259
01:03:43,470 --> 01:03:48,780
And what this means is that they will
be sent using the HTTP protocol, which

1260
01:03:48,780 --> 01:03:51,270
we've talked about endlessly
in these virtual envelopes,

1261
01:03:51,270 --> 01:03:56,190
but securely using TLS, which is
the encryption protocol that ensures

1262
01:03:56,190 --> 01:03:58,920
that no one else can see what's
going on inside of that envelope,

1263
01:03:58,920 --> 01:04:01,700
including your internet
service provider.

1264
01:04:01,700 --> 01:04:05,590
Now, someone is going to still
know what domain name you're

1265
01:04:05,590 --> 01:04:09,040
looking up because after all, to
whom are you sending this request?

1266
01:04:09,040 --> 01:04:10,990
Maybe you're sending it to Google.

1267
01:04:10,990 --> 01:04:12,910
Maybe you're sending
it to some third party.

1268
01:04:12,910 --> 01:04:14,830
But you are sending it to someone.

1269
01:04:14,830 --> 01:04:18,580
But at least, goes the thinking, it's
not your internet service provider,

1270
01:04:18,580 --> 01:04:21,095
who really doesn't need
to know this information.

1271
01:04:21,095 --> 01:04:22,720
So that's one way of thinking about it.

1272
01:04:22,720 --> 01:04:24,095
And there's alternatives to this.

1273
01:04:24,095 --> 01:04:27,760
There's actually something
called DNS over TLS, DoT, which

1274
01:04:27,760 --> 01:04:30,940
is very similar in spirit, but it
doesn't even bother using HTTP.

1275
01:04:30,940 --> 01:04:33,590
But it is still using encryption.

1276
01:04:33,590 --> 01:04:35,740
So this is something
that's increasingly common.

1277
01:04:35,740 --> 01:04:38,380
It's not necessarily the
default on a lot of systems.

1278
01:04:38,380 --> 01:04:41,200
But it's yet another feature
of today's technology

1279
01:04:41,200 --> 01:04:45,040
that you can increasingly look
for, seek out, enable proactively

1280
01:04:45,040 --> 01:04:49,000
if this, too, is a concern that you
don't necessarily want a third party,

1281
01:04:49,000 --> 01:04:52,277
like your ISP to know what
it is you're accessing.

1282
01:04:52,277 --> 01:04:53,860
And it might not even be your own ISP.

1283
01:04:53,860 --> 01:04:58,090
If you're on the road, in a
coffee shop that gives Wi-Fi,

1284
01:04:58,090 --> 01:05:00,760
or an airport that gives
Wi-Fi, at that point,

1285
01:05:00,760 --> 01:05:02,860
your internet service
provider is effectively

1286
01:05:02,860 --> 01:05:04,810
that coffee shop or that airport.

1287
01:05:04,810 --> 01:05:07,570
And do you really want them
knowing everywhere you're going?

1288
01:05:07,570 --> 01:05:10,870
You might be, depending on
your comfort level, prefer--

1289
01:05:10,870 --> 01:05:15,550
you might be preferring that, at
least, all of your DNS requests

1290
01:05:15,550 --> 01:05:19,940
go to some other central party that
you do trust for whatever reason,

1291
01:05:19,940 --> 01:05:23,140
so you're not just informing every
different Wi-Fi hotspot that you

1292
01:05:23,140 --> 01:05:25,630
might be using around the world.

1293
01:05:25,630 --> 01:05:27,880
Let me pause here and see
if there's any questions now

1294
01:05:27,880 --> 01:05:33,910
about DNS and this concern with respect
to your privacy or these solutions

1295
01:05:33,910 --> 01:05:34,960
there to.

1296
01:05:34,960 --> 01:05:41,410
AUDIENCE: Can DND [INAUDIBLE]
used to deceive users and steal

1297
01:05:41,410 --> 01:05:42,865
information, which is sensitive?

1298
01:05:42,865 --> 01:05:43,990
DAVID J. MALAN: Absolutely.

1299
01:05:43,990 --> 01:05:47,200
So DNS, itself, can also
be used for evil purposes.

1300
01:05:47,200 --> 01:05:51,265
If you control the DNS server, you
don't have to give an honest answer.

1301
01:05:51,265 --> 01:05:54,460
If someone asks you for the
IP address of harvard.edu,

1302
01:05:54,460 --> 01:05:58,600
you could give them the IP address
of some completely malicious server

1303
01:05:58,600 --> 01:05:59,800
that you control.

1304
01:05:59,800 --> 01:06:05,350
However, if the user, like Ryan,
in this case, is using HTTPS,

1305
01:06:05,350 --> 01:06:10,150
the whole point of HTTPS is to encrypt
the data between browser and server.

1306
01:06:10,150 --> 01:06:11,980
And presumably, the
browser is going to try

1307
01:06:11,980 --> 01:06:18,320
to request the TLS certificate
of harvard.edu in this case.

1308
01:06:18,320 --> 01:06:22,360
But if the IP address
returns the wrong certificate

1309
01:06:22,360 --> 01:06:26,470
that wasn't signed by the right
website, then the connection might fail.

1310
01:06:26,470 --> 01:06:29,800
And you'll be given a warning that you
can typically ignore in your browser.

1311
01:06:29,800 --> 01:06:33,010
But this should be preventable
because you should at least be warned

1312
01:06:33,010 --> 01:06:34,870
that that is not working correctly.

1313
01:06:34,870 --> 01:06:37,180
And ISPs actually do this quite often.

1314
01:06:37,180 --> 01:06:41,260
If you make a typographical error
sometimes on home networks, or coffee

1315
01:06:41,260 --> 01:06:45,490
shops, or airports, you might actually
still see a website of search results,

1316
01:06:45,490 --> 01:06:46,990
or worse, advertisements.

1317
01:06:46,990 --> 01:06:50,590
And that's because even if you made
a typo in the domain name, the coffee

1318
01:06:50,590 --> 01:06:52,840
shop's or the airport's
DNS server is still

1319
01:06:52,840 --> 01:06:55,360
going to return to you an
IP address of their server,

1320
01:06:55,360 --> 01:06:59,210
so they can at least
push some content at you.

1321
01:06:59,210 --> 01:07:02,710
So let's consider some of
the mechanisms via which

1322
01:07:02,710 --> 01:07:06,478
we can push back on some of these
more invasive privacy practices.

1323
01:07:06,478 --> 01:07:08,770
And one is something we've
talked about before, namely,

1324
01:07:08,770 --> 01:07:13,930
a virtual private network, or VPN, which
is a increasingly familiar technology.

1325
01:07:13,930 --> 01:07:16,450
But it's worth knowing
exactly what problems it is

1326
01:07:16,450 --> 01:07:18,730
solving for you and
exactly which problems

1327
01:07:18,730 --> 01:07:21,820
it is not, particularly, if
you're using such a service

1328
01:07:21,820 --> 01:07:23,890
to protect your own privacy.

1329
01:07:23,890 --> 01:07:25,220
Well, what is a VPN?

1330
01:07:25,220 --> 01:07:28,030
It allows us, recall,
to connect from point A

1331
01:07:28,030 --> 01:07:32,830
to another point B using a
completely encrypted tunnel.

1332
01:07:32,830 --> 01:07:35,740
So it doesn't matter if there
are machines in the middle,

1333
01:07:35,740 --> 01:07:37,450
as indeed, there will
be on the internet.

1334
01:07:37,450 --> 01:07:42,520
All of the traffic between A and B
on a VPN is encrypted or scrambled.

1335
01:07:42,520 --> 01:07:43,850
So what does this do?

1336
01:07:43,850 --> 01:07:47,320
This allows you to access sometimes
a corporate network or a university

1337
01:07:47,320 --> 01:07:49,750
network that might have
servers or services that

1338
01:07:49,750 --> 01:07:53,080
are only accessible if
you are on physically

1339
01:07:53,080 --> 01:07:56,560
or if you are on virtually
that particular network.

1340
01:07:56,560 --> 01:08:01,010
This ensures that even if you're at
home, or in a cafe, or an airport,

1341
01:08:01,010 --> 01:08:03,770
at least, you have an encrypted,
more secure connection

1342
01:08:03,770 --> 01:08:07,640
to the campus or the corporate network,
at which point, the campus or company

1343
01:08:07,640 --> 01:08:11,262
might be more comfortable with
you accessing those services.

1344
01:08:11,262 --> 01:08:13,220
Now, this does not prevent
you still from being

1345
01:08:13,220 --> 01:08:17,526
hacked because if you're running malware
on your own computer accidentally,

1346
01:08:17,526 --> 01:08:20,359
it doesn't matter if you have an
encrypted connection to the company

1347
01:08:20,359 --> 01:08:21,170
or campus.

1348
01:08:21,170 --> 01:08:25,250
You might very well have an infected
connection now to the company or campus

1349
01:08:25,250 --> 01:08:27,200
if you, yourselves, are infected.

1350
01:08:27,200 --> 01:08:30,680
VPNs can also be used to create
the illusion that you're actually

1351
01:08:30,680 --> 01:08:32,779
in one country and not another.

1352
01:08:32,779 --> 01:08:33,319
Why?

1353
01:08:33,319 --> 01:08:38,000
Well, if point A is where you are and
point B is somewhere abroad, well,

1354
01:08:38,000 --> 01:08:40,340
to the rest of the
world, if you start using

1355
01:08:40,340 --> 01:08:44,240
this VPN, this virtual
private network, you

1356
01:08:44,240 --> 01:08:48,380
will appear to have an IP address
that is in that foreign country

1357
01:08:48,380 --> 01:08:52,460
because all of your internet traffic
for chatting, video conferencing,

1358
01:08:52,460 --> 01:08:55,880
the web will be sent
through that VPN by design.

1359
01:08:55,880 --> 01:08:57,290
That's what a VPN is for.

1360
01:08:57,290 --> 01:09:00,149
And it will come out the other
end in that foreign country

1361
01:09:00,149 --> 01:09:06,210
and then continue on its way to the
chat service, the email service, the web

1362
01:09:06,210 --> 01:09:07,990
service, or the like.

1363
01:09:07,990 --> 01:09:10,529
So each of those services
will think that you

1364
01:09:10,529 --> 01:09:15,149
live or are physically in that foreign
country, even if you are not actually.

1365
01:09:15,149 --> 01:09:17,040
So what's the implication of this?

1366
01:09:17,040 --> 01:09:19,950
A virtual private
network only guarantees

1367
01:09:19,950 --> 01:09:23,430
that the connection between you
and that point B is encrypted.

1368
01:09:23,430 --> 01:09:26,130
It doesn't necessarily mean that
once you're out of that VPN,

1369
01:09:26,130 --> 01:09:30,149
it's going to stay encrypted,
especially if you're using still HTTP

1370
01:09:30,149 --> 01:09:31,529
and not HTTPS.

1371
01:09:31,529 --> 01:09:35,040
But it does, at least, encrypt
everything between points A and B.

1372
01:09:35,040 --> 01:09:39,158
It also does change what your
IP address appears to be,

1373
01:09:39,158 --> 01:09:41,700
so that you will, indeed, appear
to have an IP address that's

1374
01:09:41,700 --> 01:09:45,189
from that foreign country and
not your domestic IP address,

1375
01:09:45,189 --> 01:09:47,670
which might have some value
in covering your tracks

1376
01:09:47,670 --> 01:09:50,340
or decreasing the probability
that you'll be identified.

1377
01:09:50,340 --> 01:09:53,279
But again, we've seen so
many other mechanisms today,

1378
01:09:53,279 --> 01:09:55,620
whereby, your browser
can be fingerprinted

1379
01:09:55,620 --> 01:09:58,020
in the context of the web,
that someone might still

1380
01:09:58,020 --> 01:10:01,440
be able to realize that, OK,
your IP is different today,

1381
01:10:01,440 --> 01:10:04,560
but this still looks like you,
even if they don't necessarily

1382
01:10:04,560 --> 01:10:07,990
know that you are David
Malan or you, yourself.

1383
01:10:07,990 --> 01:10:11,940
But it, at least, does solve at least
one problem, which is encrypting end

1384
01:10:11,940 --> 01:10:14,430
to end all of your traffic.

1385
01:10:14,430 --> 01:10:16,380
Well, there's another
piece of software that's

1386
01:10:16,380 --> 01:10:19,900
been popular for some time
called Tor, The Onion Router.

1387
01:10:19,900 --> 01:10:24,030
So this is a piece of software that
you can install on your own Mac, or PC,

1388
01:10:24,030 --> 01:10:25,230
or other device.

1389
01:10:25,230 --> 01:10:30,210
And this uses encryption to solve
the problem a different way using

1390
01:10:30,210 --> 01:10:35,100
additional encryption to try to give
you a higher probability of privacy.

1391
01:10:35,100 --> 01:10:38,070
And here's a picture that Tor,
themselves, puts on their website.

1392
01:10:38,070 --> 01:10:41,310
And it has depicting here
you on a very old school

1393
01:10:41,310 --> 01:10:44,910
PC connecting to a whole
bunch of nodes inside

1394
01:10:44,910 --> 01:10:47,520
of this Tor network
connected to ultimately maybe

1395
01:10:47,520 --> 01:10:49,230
the websites that you're visiting.

1396
01:10:49,230 --> 01:10:54,900
And what happens here is that when your
computer is running the Tor software,

1397
01:10:54,900 --> 01:10:57,990
the Tor software first figures
out, OK, who else in the world

1398
01:10:57,990 --> 01:10:59,730
is using the Tor software?

1399
01:10:59,730 --> 01:11:03,510
Because it's going to use those other
computers to route your traffic,

1400
01:11:03,510 --> 01:11:07,050
up, down, left, and right and
kind of like the movies or TV,

1401
01:11:07,050 --> 01:11:11,508
where you see a map of the world and
the traffic is bouncing back and forth

1402
01:11:11,508 --> 01:11:12,300
and back and forth.

1403
01:11:12,300 --> 01:11:14,400
That's kind of the spirit of Tor.

1404
01:11:14,400 --> 01:11:17,250
And what happens is
if your computer here

1405
01:11:17,250 --> 01:11:23,010
wants to send a request to a
website that's maybe over here

1406
01:11:23,010 --> 01:11:25,530
and it decides, for instance,
to route it through one,

1407
01:11:25,530 --> 01:11:29,610
two, three computers, what
the Tor software will do

1408
01:11:29,610 --> 01:11:33,240
is encrypt the request at
least three different times.

1409
01:11:33,240 --> 01:11:36,600
Whatever web request you are
sending, whatever email you

1410
01:11:36,600 --> 01:11:39,630
are sending, whatever chat message
you're sending, whatever service you

1411
01:11:39,630 --> 01:11:43,110
are using between point A on the
left and point B on the right

1412
01:11:43,110 --> 01:11:47,310
is going to be encrypted
with this node's public key,

1413
01:11:47,310 --> 01:11:51,600
with this node's public key,
with this node's public key.

1414
01:11:51,600 --> 01:11:54,930
And so here's the onion
in Tor, The Onion Router.

1415
01:11:54,930 --> 01:11:59,140
You are encrypting layer, upon
layer, upon layer of data,

1416
01:11:59,140 --> 01:12:03,750
so that mathematically, recall per our
discussion of public key cryptography,

1417
01:12:03,750 --> 01:12:07,230
only this node can peel
off one layer, only

1418
01:12:07,230 --> 01:12:11,220
this node can peel off one layer, only
this node can peel off one layer using

1419
01:12:11,220 --> 01:12:15,810
their own respective private keys,
which undoes the effect of your

1420
01:12:15,810 --> 01:12:17,710
having encrypted your traffic.

1421
01:12:17,710 --> 01:12:19,920
So what you're really
doing here by choosing,

1422
01:12:19,920 --> 01:12:23,730
perhaps, a different path, every
request, a different path every day

1423
01:12:23,730 --> 01:12:27,570
is you are with Tor effectively
covering your tracks in some sense.

1424
01:12:27,570 --> 01:12:32,290
And by design, the Tor software doesn't
remember much information at all,

1425
01:12:32,290 --> 01:12:35,580
so it doesn't have the sorts of logs
that I propose can be worrisome,

1426
01:12:35,580 --> 01:12:37,260
at least, in the context of web servers.

1427
01:12:37,260 --> 01:12:41,710
By design, Tor is meant to preserve
your privacy with higher probability.

1428
01:12:41,710 --> 01:12:45,060
And so by design, it just doesn't keep
nearly as much information around.

1429
01:12:45,060 --> 01:12:48,850
Now, this isn't to say that if you're
doing this for malicious purposes,

1430
01:12:48,850 --> 01:12:50,910
trying to evade the
authorities, this isn't

1431
01:12:50,910 --> 01:12:53,700
to say that this computer,
this computer, this computer

1432
01:12:53,700 --> 01:12:57,000
couldn't be subpoenaed, so to
speak, by some government entity

1433
01:12:57,000 --> 01:13:00,910
and they could reconstruct
the path that your data took.

1434
01:13:00,910 --> 01:13:03,790
But the point is that it's
generally quite laborious.

1435
01:13:03,790 --> 01:13:07,720
By this time, all of that data has
disappeared from those interior nodes.

1436
01:13:07,720 --> 01:13:09,820
And so they don't have
much information to share.

1437
01:13:09,820 --> 01:13:14,740
And so increasingly, it does provide you
with some higher probability of privacy

1438
01:13:14,740 --> 01:13:18,520
by layering your requests with
encryption, encryption, encryption

1439
01:13:18,520 --> 01:13:21,220
and sort of trusting that
these interior nodes are

1440
01:13:21,220 --> 01:13:24,895
going to relay it to the
final endpoint, so something

1441
01:13:24,895 --> 01:13:26,020
to consider if of interest.

1442
01:13:26,020 --> 01:13:30,400
But realize, too, that because of how
the internet works with IP addresses,

1443
01:13:30,400 --> 01:13:32,800
because of how the internet
works with port numbers,

1444
01:13:32,800 --> 01:13:38,360
it's still possible on a network to
know who is using Tor, for instance.

1445
01:13:38,360 --> 01:13:43,360
So if you happen to be the only person
at home, the only person on a company

1446
01:13:43,360 --> 01:13:46,990
or on a university network
who's using Tor at the moment,

1447
01:13:46,990 --> 01:13:50,230
it's being used for
malicious purposes, odds are,

1448
01:13:50,230 --> 01:13:53,840
you could be targeted as
the source of that attack.

1449
01:13:53,840 --> 01:13:58,150
And so realize, in particular, that
this just raises the bar to detection.

1450
01:13:58,150 --> 01:14:01,320
It raises the bar to your
privacy being invaded.

1451
01:14:01,320 --> 01:14:05,870
But it does not, as do none of
the technologies we've discussed,

1452
01:14:05,870 --> 01:14:10,120
give you an absolute protection
of these same properties.

1453
01:14:10,120 --> 01:14:13,740
So there's one final mechanism when
it comes to preserving one's privacy

1454
01:14:13,740 --> 01:14:16,230
that's thankfully
increasingly available to us

1455
01:14:16,230 --> 01:14:19,800
on devices, on desktops and
laptops, and especially, on phones.

1456
01:14:19,800 --> 01:14:23,190
And that's this notion of
permissions, which isn't anything new.

1457
01:14:23,190 --> 01:14:26,910
But as iOS, and Android,
and other operating systems

1458
01:14:26,910 --> 01:14:31,440
have evolved, increasingly, you and
I are being asked by our operating

1459
01:14:31,440 --> 01:14:34,110
systems, do you want to allow this?

1460
01:14:34,110 --> 01:14:36,840
Not only do you want to
allow this program to run,

1461
01:14:36,840 --> 01:14:40,980
but do you want to allow this program
to access your camera, for instance?

1462
01:14:40,980 --> 01:14:44,040
Do you want this program to access
your microphone, for instance?

1463
01:14:44,040 --> 01:14:48,940
Do you want this application to
access your contacts, for instance?

1464
01:14:48,940 --> 01:14:53,310
So on the one hand, we're being
given much more fine-grained control,

1465
01:14:53,310 --> 01:14:55,830
which is a good thing, presumably.

1466
01:14:55,830 --> 01:15:00,240
At the same, time, it's also just
pushing the decision onto you and me.

1467
01:15:00,240 --> 01:15:03,450
And very often, with these applications,
as you've probably found, well,

1468
01:15:03,450 --> 01:15:07,140
if you don't enable the camera
and give access to the app,

1469
01:15:07,140 --> 01:15:10,840
it just might not work because they
have some code in their application

1470
01:15:10,840 --> 01:15:14,870
that says if camera's not on,
then do not do anything useful.

1471
01:15:14,870 --> 01:15:19,030
So there's this tension between
usability and privacy in this case.

1472
01:15:19,030 --> 01:15:21,460
But thankfully, there's
finer-grained controls too.

1473
01:15:21,460 --> 01:15:23,570
On iOS, for instance,
you might be prompted,

1474
01:15:23,570 --> 01:15:26,290
do you want to give this
app access to this feature

1475
01:15:26,290 --> 01:15:30,722
always, or only while using
the application, or never?

1476
01:15:30,722 --> 01:15:32,680
And that's certainly a
good thing for something

1477
01:15:32,680 --> 01:15:34,840
like the camera or the
microphone, where it

1478
01:15:34,840 --> 01:15:37,090
would be nice to trust
that when you close the app

1479
01:15:37,090 --> 01:15:39,730
and put your phone in your
pocket, that it's not still

1480
01:15:39,730 --> 01:15:43,440
listening to or trying to watch
you from this built-in hardware.

1481
01:15:43,440 --> 01:15:45,190
Now, there is some
feature that might need

1482
01:15:45,190 --> 01:15:48,940
to run all of the time, which includes
location-based services, which

1483
01:15:48,940 --> 01:15:51,340
is to say that our phones,
especially nowadays,

1484
01:15:51,340 --> 01:15:54,880
can pretty effectively track
our location using GPS,

1485
01:15:54,880 --> 01:15:57,100
or Wi-Fi, or some other technology.

1486
01:15:57,100 --> 01:16:00,910
Now, that's of course, useful, if
not, necessary for using mapping

1487
01:16:00,910 --> 01:16:03,850
applications, like Maps, or
Google Maps, or the like that

1488
01:16:03,850 --> 01:16:08,110
help us get physically from point
A to point B. But very commonly,

1489
01:16:08,110 --> 01:16:10,360
these applications,
at least, by default,

1490
01:16:10,360 --> 01:16:13,960
ask for access to your
geographic location

1491
01:16:13,960 --> 01:16:17,260
always, which means just
by walking down the street,

1492
01:16:17,260 --> 01:16:19,790
even if you're not following
a map on your phone,

1493
01:16:19,790 --> 01:16:22,870
means that the app can still
be tracking where you're going.

1494
01:16:22,870 --> 01:16:25,360
And certainly, among the
Googles and the Apples

1495
01:16:25,360 --> 01:16:27,700
of the world nowadays
or other manufacturers,

1496
01:16:27,700 --> 01:16:30,640
they certainly know
pretty much everywhere you

1497
01:16:30,640 --> 01:16:35,600
and I are going if we leave these
location-based services on by default.

1498
01:16:35,600 --> 01:16:40,900
So this is an example of something of
which you should be mindful if only

1499
01:16:40,900 --> 01:16:43,900
because here is yet another
example of information

1500
01:16:43,900 --> 01:16:48,130
that logically, when you think about
it, OK, obviously, that makes sense.

1501
01:16:48,130 --> 01:16:51,280
They must be keeping track
of my location, otherwise,

1502
01:16:51,280 --> 01:16:54,250
how could they provide
me with mapping services?

1503
01:16:54,250 --> 01:16:58,030
But pause and think now, perhaps,
exactly what the implications

1504
01:16:58,030 --> 01:17:02,260
are for you, for your privacy,
and just walking around 24/7

1505
01:17:02,260 --> 01:17:05,830
with these radios now in our pockets.

1506
01:17:05,830 --> 01:17:08,950
So even though there are quite
a few threats to our privacy,

1507
01:17:08,950 --> 01:17:11,860
online especially, at least,
there are these mechanisms

1508
01:17:11,860 --> 01:17:16,360
that you and I can enable to at
least preserve some of the same.

1509
01:17:16,360 --> 01:17:18,670
Well, what have we done
over the past few weeks?

1510
01:17:18,670 --> 01:17:21,580
We began with a look at how we
can secure our accounts, then

1511
01:17:21,580 --> 01:17:24,520
our data, then our systems, then
our software, and today, of course,

1512
01:17:24,520 --> 01:17:26,930
focusing on preserving our privacy.

1513
01:17:26,930 --> 01:17:29,770
And by way of the various
technologies we've looked at,

1514
01:17:29,770 --> 01:17:33,700
the stories we've told, the
principles that we've introduced,

1515
01:17:33,700 --> 01:17:36,610
we hope that in the days,
the weeks, and the years

1516
01:17:36,610 --> 01:17:39,700
to come, you can use all
of these first principles,

1517
01:17:39,700 --> 01:17:41,470
and these ideas, and
these building blocks

1518
01:17:41,470 --> 01:17:44,140
to extrapolate to how
new technologies work,

1519
01:17:44,140 --> 01:17:48,580
to how new threats might affect you, and
to what questions you should be asking

1520
01:17:48,580 --> 01:17:53,110
of either the software you use or
the software you develop to ensure

1521
01:17:53,110 --> 01:17:56,290
that not only your communications
are secure, but also,

1522
01:17:56,290 --> 01:18:00,850
that it has these privacy-preserving
properties that you, and your users,

1523
01:18:00,850 --> 01:18:02,560
and your customers might want.

1524
01:18:02,560 --> 01:18:05,860
This then was CS50's
Introduction to Cyber Security.

1525
01:18:05,860 --> 01:18:08,640
And this was CS50.

1526
01:18:08,640 --> 01:18:12,000