Mozilla security policy cracks down on creepy web trackers, holds supercookies over fire

Firefox maker sets out dodgy practices the browser will block

The Mozilla Foundation has announced its intent to reduce the ability of websites and other online services to track users of its Firefox browser around the internet.

At this stage, Moz's actions are baby steps. In support of its decision in late 2018 to reduce the amount of tracking it permits, the organisation has now published a tracking policy to tell people what it will block.

Moz said the focus of the policy is to bring the curtain down on tracking techniques that "cannot be meaningfully understood or controlled by users".

Notoriously intrusive tracking techniques allow users to be followed and profiled around the web. Facebook planting trackers wherever a site has a "Like" button is a good example. A user without a Facebook account can still be tracked as a unique individual as they visit different news sites.

Mozilla's policy said these "stateful identifiers are often used by third parties to associate browsing across multiple websites with the same user and to build profiles of those users, in violation of the user's expectation". So, out they go.

Of course, that's not the only technique used for cross-site tracking. As detailed in Mozilla's policy, some sites "decorate" URLs with user identifiers to make the user identity available to other websites.

Firefox isn't yet ready to block that kind of behaviour, but Mozilla said: "We may apply additional restrictions to the third parties engaged in this type of tracking in future."

Sites will be able to use URL parameters for activities such as advertisement conversion tracking, the policy said, so long as that isn't abused to identify individuals.

Mozilla has also flagged browser fingerprinting (tagging an individual by the fonts they have installed is the most familiar example) and supercookies for future removal.

The "may block in the future" nature of the policy seems depressingly conditional, but independent cybersecurity researcher Dr Lukasz Olejnik told The Register the effort is at least an indication that Mozilla is taking user privacy seriously.

"After months of studies and preparation, Mozilla decided to take a hard stance on certain kinds of tracking measures," he said. "Firefox will begin the blocking of scripts behaving in an unacceptable manner, such as as tracking or unconventional methods of identification via fingerprinting. It is... sending a strong message that the misuse of certain web browser features is no longer welcome.

"Certain script activity will keep working if user action indicates a clear intention, such as clicking on a link." ®

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