With the release of version 67 of Firefox, which is scheduled for May 2019, Mozilla is set to add a new anti-fingerprinting method for users to maintain anonymity while browsing.
The concept of the new feature was originally developed for the Tor browser four years ago.
Mozilla’s goal is to guarantee the privacy and anonymity of internet users around the world. In order to do this, it wants to eliminate any risk of monitoring and data collection by advertising agencies and site publishers.
What Is Fingerprinting?
The abovementioned advertising agencies and site operators generally use browsing history and cookies as a way to identify and track users.
This data is no longer accessible in the case where users browse in private mode.
In this situation, however, the trackers hijack this obstacle using a method known as fingerprinting, which consists of recovering data on the fonts, plugins and windows displayed on the screen.
This type of data gives the user a unique identity and thus it allows for the site publishers and advertising agencies to collect more data the user.
It is a powerful technique that websites use to collect information about the user’s operating system, browser type and version, time zone, screen resolution, language and other active settings.
Although it may seem generic at first glance and insufficient to identify a specific person, there’s a really small chance for another user to have exactly the same matching browser information.
A recent report [PDF] by the Electronic Frontier Foundation discovered that 1 in 286,777 browsers have the same fingerprint as another user.
A Method to Boost Anonymity for Firefox Users
This problem is set to be addressed soon thanks to Mozilla’s ongoing collaboration with Tor.
As the Tor browser is based on Firefox’s Extended Support Release version, Firefox has often adopted privacy features used by Tor in the past.
The letterboxing concept was originally developed for the Tor browser back in 2015.
The letterboxing function inserts gray spaces to a webpage’s sides when the user changes the size of the window.
The fundamental concept of letterboxing is that it will hide the window’s real dimensions during the window resize operation by keeping the window height and width at multiples of 100px and 200px.
It will generate the same dimensions of the window for all users, and a gray space will be added at the bottom, top, right or left of the current page.
Listening to the window rescale events, the ad system will then read the generic dimension and send the data to its servers.
What letterboxing will actually do is trick the advertising code into seeing the recently rescaled browser window at inaccurate dimensions.
The window can have any size and shape, but the content of the page inside it is only shown at certain preset dimension; the rest is occupied with gray space.
A spokesperson for Mozilla commented to say that the Letterbox experiment is a bit different from the previous experiment which was carried out by the Tor browser.
The upcoming feature involves using gray spaces to keep the page content at a preset dimension, while the Tor browser’s method was to keep the whole browser window at preset dimensions.