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Mozilla Firefox 67 will allow letterboxing to protect your online identity

GeneralEdward Kiledjian2 Comments

September 2016 I wrote an article entitles “Your browser will betray your identity” that discussed the various techniques legitimate (marketers) and illegitimate (threat actors) use to keep track of your identity even if you aren’t logged into any of their sites.

The purpose-built TOR version of the Mozilla Firefox browser has (for a while) implemented a technique called letterboxing to protect users from this type of nefarious identification through browser fingerprinting.

Most browsers allow a site to send client-side javascript code that detects the display size of the browser. This technique is used to create dynamically generated webpages that are optimized for the device size you are using. This is why modern well-designed websites render correctly on large 24" desktop screens and 6" smartphones.

Would you be surprised to learn that this can be one dimension threat actors or marketers can use to start deanonymizing you?

The privacy team behind the TOR project goes to great lengths to maximize your privacy while using their anonymizing network by minimizing your data exhaust while browsing the web. We have seen the Firefox team backport some of these privacy enhancements back into the mainstream Firefox. This backport initiative is called TOR Uplift and started in 2016.

In release 67, expected in May, Firefox will bring letterboxing into the mainstream version (from the TOR one). Letterboxing is a technique of rounding the actual size of the browser window (height and width) down to a multiple of 200 pixels for width and 100 pixels for height. This means more users will have the same window size value making deanonymizing more complicated. Firefox will add grey bars on a side that needs to be padded if the rendered page isn't a perfect fit. If you are more concerned about looks, you will be able to turn off this additional protection technique using a Firefox flag.

In the Bugzilla tracker, Mozilla wrote "Window dimensions are a big source of fingerprintable entropy on the web" & "Maximized windows reveal available screen width and height, excluding toolbars; and full-screen windows reveal screen width and height. Non-maximized windows can allow a strong correlation between two tabs".

Here is a demo of letterboxing while resizing the browser window. Notice the grey added around the rendered page.

The letterboxing feature won’t be turned on by default. Users wanting this extra layer of protection will have to open about:config and enter “privacy.resistFingerprinting” in the config search box and change the setting to “true”.

The New York Times now available on TOR

GeneralEdward KiledjianComment
I do not agree with what you have to say, but I’ll defend to the death your right to say it.
— Voltaire

When the average consumer thinks about TOR (which isn't very often), they imagine that it is the ugly, damp & rancid underbelly of the internet. 

Reality is that TOR is a US government-funded project to create anonymity on the internet. It is a platform that allows everyone to have a voice without fear of punishment or even death (think political activists).

No technology is perfect, but TOR is a very powerful tool for human rights activists and other dissidents. 

In a 2015 The Intercept article, Edward Snowden goes as far as saying "I think Tor is the most important privacy-enhancing technology project being used today. " & " What Tor does is it provides a measure of security and allows you to disassociate your physical location."

Proof that TOR isn't just for drugs and counterfeit goods is the fact many reputable organizations have started to create their own TOR presence. 

The New York times launched it's TOR Onion Service website (in late October) as a secure way of making its content available to people around the world that may otherwise not have access to its content (China, Iran, etc.)

When companies moved to the web 15-20 years ago, sites were less reliable as companies tried to figure out how this "web thing" worked. TOR is the same today. Sites Like the New York Times are still trying to figure out how to efficiently use TOR, and therefore you should assume these sites are all in beta status. 

The New York Times reports on stories all over the world, and our reporting is read by people around the world. Some readers choose to use Tor to access our journalism because they’re technically blocked from accessing our website; or because they worry about local network monitoring; or because they care about online privacy; or simply because that is the method that they prefer.
— The New York Times

You can access The New York Times TOR ONION Service site here : https://www.nytimes3xbfgragh.onion/ [remember this doesn't work via the "normal web".