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Evercookie: A cookie that undeletes itself from 8 different storages

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Re: Evercookie: A cookie that undeletes itself from 8 different storages

#42

Post by StavrosK »

naturalized wrote: post #35

I know that in Chrome's incognito mode, nothing gets written to the disk at all (including Flash's Shared Objects). So if I open an incognito window, browse, then close Chrome, then open another incognito window and return to the page, does this defeat all this?

Why doesn't anyone try this? I did, and it seems that incognito mode does defeat this. However, since this always sets the same cookie, I couldn't tell if it read it or set it. From the looks of things, it only read the cookie, which means that closing incognito mode deletes it.

Re: Evercookie: A cookie that undeletes itself from 8 different storages

#43

Post by sorbus »

phil wrote: post #34
xtacy wrote: post #29

So by default, I should be browsing every site in Incognito/private browsing mode, then.

Will that defeat Flash storage and the PNG caching trick, too?

Well, if you're not writing anything to disk, nothing should get cached. So PNG caching wouldn't work. But I'm not so sure about flash storage ... if it's using a bit of flash to store that, then flashblock should stop it, if it's allowed to run in incognito, but if there's some other way then perhaps not.

Re: Evercookie: A cookie that undeletes itself from 8 different storages

#47

Post by atldev »

naturalized wrote: post #35

I know that in Chrome's incognito mode, nothing gets written to the disk at all (including Flash's Shared Objects). So if I open an incognito window, browse, then close Chrome, then open another incognito window and return to the page, does this defeat all this?

Nope, just tried it. Incognito, cookies there. Clear cache, incognito mode again and 3 types still captured. Really quite fascinating.

Re: Evercookie: A cookie that undeletes itself from 8 different storages

#48

Post by nl »

mey wrote: post #27
nl wrote: post #21

Earlier quoted context omitted.

Thinking about it a bit more, it's actually worse than that. http://www.nihilogic.dk/labs/imageinfo/ shows how to extract EXIF data from JPEG files, so using EXIF + the cache hack is possible for sure. http://www.nihilogic.dk/labs/id3/ shows how to extract ID3 metadata from MP3s in Javascript, so you could do a similar thing like that. Can anyone think why just using the cache hack + a JSON data file wouldn't work?

It's even worse then that. http://en.wikipedia.org/wiki/Steganography That slightly larger in disk size logo on the main site could be hiding a tracking token for you....

It's unlikely they'd use a logo, because of the brittleness of the technique (ie, it relies on sending 304 Not Modified response due to the absence of the special tracking cookie, not due to the actual cache status).

Also, it's not clear if you get access to the actual binary data from the image as it is served, or new data generated from the image as it is displayed - hence my question as to if using the metadata would work.

Re: Evercookie: A cookie that undeletes itself from 8 different storages

#49

Post by naturalized »

atldev wrote: post #47
naturalized wrote: post #35

I know that in Chrome's incognito mode, nothing gets written to the disk at all (including Flash's Shared Objects). So if I open an incognito window, browse, then close Chrome, then open another incognito window and return to the page, does this defeat all this?

Nope, just tried it. Incognito, cookies there. Clear cache, incognito mode again and 3 types still captured. Really quite fascinating.

Did you completely quit the browser in between your visits? Because if the instance of Chrome from which you opened the incognito windows have been running between your visits, it may have retrieved these from the memory, even if you closed the incognito window after the first visit.
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