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Un-killable 'Evercookie' Killed ... Sometimes
Trailrunner7 writes "The persistent method that security researcher Samy Kamkar introduced last week for storing tracking data on a user's machine, known as the 'Evercookie,' is even more worrisome when used on mobile devices, according to another researcher's analysis. The Evercookie is a simple method for forcing a user's machine to retain browser cookies by storing the data in a number of different locations. The method also has the ability to recreate deleted cookies if it finds that the user has removed them. Created by Kamkar as a demonstration of a way that sites could use to persistently track users even after they clear their browser cookies, the Evercookie has drawn the attention of a number of other researchers who have spent some time looking for methods to defeat it. A researcher in South Africa took a look at the way the the Evercookie works on both Safari on the desktop and on mobile devices, and found that it can be undone in some circumstances. However, he also found that the mobile version of Safari fares far worse in its handling of the Evercookie than the standard version does."
While it is not un-killable, it is pretty much a pain in the ass to get rid of, since it will get back if you miss a single one and visit the site again.
Didn't we used to call this kind of stuff "malware"? When did it become acceptable, no matter how annoying or unwanted the user is, to put something on their computer without their knowledge that is hard or near-impossible to remove?
That's not the solution. The whole point of the "evercookie" is that it doesn't just use regular HTTP cookies to store information, but also abuses all kinds of common browser features related to CSS, caching, embedded Flash objects and anything else that can be exploited to store state. If all he did was store a cookie only, then any browser worth its salt could easily purge it from the browser history.
So even if you just block cookies, that doesn't prevent this hack to work. You may need to block a whole range of features from JavaScript to HTTP caching to Flash support. It's certainly possible, but not something that an average user is prepared to do.