Firefox web browser version 67 could include a new anti-fingerprintin technique which protects against certain fingerprinting methods used related to the size of the web browser window.
Fingerprinting is a technique to identify and track the user or mobile user based on a unique fingerprint, websites can use various parameters. For example, they can go through the enumeration of browser plugins, the variable "user agent", the list of sources on your system, and so on.
The technique comes from experiments conducted by the developers of the Tor browser and is part of the Tor Uplift project started in July 2016. The goal of this project is to improve the privacy protection features of Firefox by relying on those of tor.
All the Ad networks often detect certain browser functions, such as window size, to create user profiles and keep track of users as they resize their browser and move between new URLs and browser tabs.
About letterboxing
Called «letterboxing», this new technique adds "gray spaces" to the sides of a web page when the user resizes the browser window, which are then phased out once the window resize operation is complete.
The general idea is that "Letterboxing" will hide the actual dimensions of the window keeping the width and height of the window in multiples of 200px and 100px during the resize operation, generating the same window dimensions for all users and then adding a "gray space" at the top, bottom, left or right of the current page.
Letterboxing is not a new technique. Mozilla is integrating a feature that was originally developed for the Tor browser four years ago, in January 2015.
However, the feature is not enabled by default.
Firefox users will first have to go to the page about:config and search "Privacy.resistFingerprinting" in the search field and here you must change the browser's "anti-fingerprinting" functions to "true".
Support for this new feature to be added to Firefox 67 not only works when resizing a browser window, but also when users maximize the browser window or switch to full screen mode.
For those who are interested in Letterboxing should know that is currently available on Firefox Nightly y It will be available in a stable version of the web browser for all users with the release of Firefox 67 in May.
Mozilla's fight against fingerprinting has long gone
Fingerprinting techniques have not been frowned upon by Mozilla, so Mozilla has made several moves to put an end to this.
And is that since Firefox 52, Mozilla engineers incorporated a mechanism to protect users fingerprinting that used a technique based on the list of system fonts.
Fingerprinting of fonts is based on website operators implementing Flash or JavaScript scripts that query the user's browser for a list of locally installed fonts.
Since version 58, Firefox no longer allows companies and websites that use some elements in HTML to extract user data without the consent of the latter.
In fact, the same web browser warned users when they accessed a website and the web browser detected the HTML elements, signaling to the user that these HTML tags could only be used for identification purposes. The extraction of this element could be done so far by the websites silently.
Si you want to know a little more about this new function you can check the Bugzilla entry, in which he explains how Firefox's letterboxing protection works.