Privacy Badger
was created to protect users from pervasive non-consensual tracking, and
to do so automatically, without relying on human-edited lists of known trackers. While our goals remain the same, our approach is changing. It is time for Privacy Badger to evolve.
Thanks to disclosures from Google Security Team, we are changing the way Privacy Badger works by default in order to protect you better. Privacy Badger used to learn about trackers as you browsed the Web. Now, we are turning “local learning” off by default, as it may make you more identifiable to websites or other actors. If you wish, you can still choose to opt in to local learning and have the exact same Badger experience as before. Regardless, all users will continue to benefit from Privacy Badger’s up-to-date knowledge of trackers in the wild, as well as its unique extra privacy-preserving features like
outgoing link protection and
widget replacement.
Google Security Team reached out to us in February with a set of security disclosures related to Privacy Badger’s local learning function. The first was a serious security issue;
we removed the relevant feature immediately. The team also alerted us to a class of attacks that were enabled by Privacy Badger’s learning. Essentially, since Privacy Badger adapts its behavior based on the way that sites you visit behave, a dedicated attacker could manipulate the way Privacy Badger acts: what it blocks and what it allows. In theory, this can be used to identify users (a form of
fingerprinting) or to extract some kinds of information from the pages they visit. This is similar to the
set of vulnerabilities that Safari’s Intelligent Tracking Prevention feature
disclosed and patched late last year.
To be clear: the disclosures Google’s team shared with us are purely proof-of-concept, and we have seen no evidence that any Privacy Badger users have had these techniques used against them in the wild. But as a precaution, we have decided to turn off Privacy Badger’s local learning feature by default.
From now on, Privacy Badger will rely solely on its “Badger Sett”
pre-trained list of tracking domains to perform blocking by default. Furthermore, Privacy Badger’s tracker database will be refreshed periodically with the latest pre-trained definitions. This means, moving forward, all Privacy Badgers will default to relying on the same learned list of trackers for blocking.
