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AdBlock: 'Canvas Fingerprinting' Tech Over-Hyped, Can Be Blocked
by Karl Bode 08:24AM Friday Jul 25 2014
A report over at ProPublica breathlessly proclaims this week that there's a new advertising and tracking system that's "virtually impossible to block." The technology, being developed by a company called AddThis, utilizes something called "canvas fingerprinting." Canvas fingerprinting, first discussed in a 2012 paper by Keaton Mowery and Hovav Shacham (pdf), uses your computer's unique graphics rendering capabilities (graphics card, browser, driver variant) to track your movements across the Internet --without storing any data locally.

Reliability of canvas fingerprinting has been somewhat iffy; especially on wireless networks (where device hardware and software is far more uniform), and large scale Internet use is far off if it happens at all. Still, the ProPublica report paints canvas fingerprinting as a pretty immediate threat to user privacy, and claims that tools like AdBlock won't work:
Like other tracking tools, canvas fingerprints are used to build profiles of users based on the websites they visit — profiles that shape which ads, news articles, or other types of content are displayed to them. But fingerprints are unusually hard to block: They can’t be prevented by using standard Web browser privacy settings or using anti-tracking tools such as AdBlock Plus.
Not so fast, argues AdBlock's Wladimir Palant in a blog post. Palant reiterates that canvas fingerprinting isn't really reliable enough to replace cookies, and even if it does see widespread adoption, AdBlock Plus should be able to block it just fine:
...what we have here is a potential (but not too reliable it seems) way to track users who clear cookies or block third-party cookies completely. And what about Adblock Plus? When you add the EasyPrivacy filter list in Adblock Plus this won’t make Adblock Plus block tracking cookies directly. Instead, Adblock Plus will block the script that would try to set these cookies. And guess what: blocking that script doesn’t just prevent cookie-based tracking, it also lets you deal with canvas fingerprinting or evercookie or any other tracking approach. In particular, the rules to prevent AddThis tracking were added to EasyPrivacy almost five years ago.
Even AdThis, the company that is working on the technology, states they may drop the effort because it may not be "uniquely identifying enough." As such, this new "unstoppable" and "impossible to block" ad technology doesn't appear to be much of any immediate threat.

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