Firefox introduces new tool to prevent cookie-based tracking

12. March 2021

Mozilla has announced the introduction of a new privacy tool for its Firefox browser, “Total Cookie Protection”, aimed at blocking cookie-based tracking by ad-tech companies. The new feature prevents cross-site tracking by confining cookies to the website where they were created and placing them into a so-called “cookie jar”.

Mozilla refers to cookies as “a useful technology, but also a serious privacy vulnerability” because they are shared between websites which enables tracking user’s browsing behavior. This approach allows advertising companies, in particular, to gather information about users, their browsing habits and interests as well as create detailed personal profiles.

Total Cookie Protection works by maintaining a separate “cookie jar”, assigned to each website visited. This procedure prohibits the deposited cookie from being shared with any other website. A limited exception only applies to cross-site cookies needed for non-tracking purposes.

Firefox has blocked some cookies used by ad-tech companies for years in an effort to fight against cookie abuse and web tracking. In order to achieve this goal, “Enhanced Tracking Protection” (ETP) was introduced in 2019. It blocks many of the companies identified as trackers by Mozilla’s partners at Disconnect. Despite being an effective strategy to stop tracking, this form of cookie blocking has its limitations, Johann Hofmann and Tim Huang remark on the developer blog Mozilla Hacks:

ETP protects users from the 3000 most common and pervasive identified trackers, but its protection relies on the fact that the list is complete and always up-to-date. Ensuring completeness is difficult, and trackers can try to circumvent the list by registering new domain names. Additionally, identifying trackers is a time-consuming task and commonly adds a delay on a scale of months before a new tracking domain is added to the list.

With this in view, Total Cookie Protection has been built into ETP as a new privacy advance. The feature intends to address the limitations of ETP and provide more comprehensive protection. It is complemented by Supercookie Protections rolled out last month, which shall eliminate the usage of non-traditional storage mechanisms (“supercookies”) as a tracking vector.

In conclusion, Mozilla stated:

Together these features prevent websites from being able to “tag” your browser, thereby eliminating the most pervasive cross-site tracking technique.