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."

Comments

Evercookie is clever

[Nichotin]

For forum administrators, it is a very clever way to keep many ban evaders out. 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. Read the list of the places it stores its cookies, and be amazed how many there actually are. So, 1) ban user, 2) place cookie, 3) user signs up again, 4) your site detects the evercookie + new registration, 5) verify and ban again (unless the user suddenly becomes a good user, of course).

Re:Evercookie is clever

[Anonymous Coward]

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?

Re:Evercookie is clever

[tehdaemon]

Malmarker then? Maldata? Evilbytes? I suppose at some level pedantry about word definitions makes sense, so fine, don't call it malware. But it is in the same 'badness' class as most malware, and needs an equally bad name to go with it.

T

Re:Evercookie is clever

[The Wild Norseman]

Malware is executable software. The evercookie isn't software, it's a simple marker.

The cookie resides on my hardware, doing something (tracking -- albeit doing something passively in this case) which I only wish to grant it for a limited amount of time. When the makers of this cookie make it extremely difficult to delete, which takes away the control I have over the data on my computer, then I see no practical difference between this passive cookie and active malware. Just MHO.

Re:Evercookie is clever

[pclminion]

Just put it in the ToS for the site that you use "advanced measures to track banned users." Presto, now you're not being underhanded about it, which is really the critical difference between malware and other forms of software.

Re:Evercookie is clever

[Yvan256]

If we on Slashdot start calling cookies "malware" then it's no different than when ordinary computer users don't know the difference between a virus and a trojan.

Next thing you know we have teachers who think Linux is a Windows program and that no computer can run without a Microsoft OS.

Re:Evercookie is clever

[CCarrot]

If we on Slashdot start calling cookies "malware" then it's no different than when ordinary computer users don't know the difference between a virus and a trojan.

Ordinary cookies don't actively fight removal by the user, and once they're gone, they're gone.

Ordinary (non-malware) applications don't actively fight removal by the user, and once they're gone, they're gone (okay, other than some leftover user/config data sometimes, but the program itself is gone and no longer does what it was designed to do).

The 'Evercookie', on the other hand, behaves exactly like malware in that it actively resists being deleted by the user, even to the point of rebuilding itself after deliberate removal attempts, and all for the benefit of a third party.

Re:Evercookie is clever

[Firehed]

It's a fairly complex storage mechanism, designed to get around a user's preferences. In the wrong hands, it's very dangerous. I'd certainly call it closer to malware than, for example, the recent iPhone jailbreaks - which are so kind as to patch the security flaw that let the software run in the first place. Yet by your reasoning, jailbreaking is malware and evercookies are harmless. If you think that ad retargeting (ads that basically follow you around the web) is creepy, wait until they know with 100% certainty that you're a known user in some known demographic.

Re:Evercookie is clever

[Firehed]

Putting something in the TOS to "not [be] underhanded" is, in itself, being underhanded. Or perhaps you're that one non-crawler in my server logs with the request to /about/terms, in which case I take that back.

Re:Evercookie is clever

[davidbofinger]

It's not the same concept but "malcontent" deserves to be coined.

If only...

[NoobixCube]

I wish I had an evercookie. A magical cookie that regrows every time you take a bite out of it sounds like an amazing idea.

Re:If only...

[Anne_Nonymous]

You shit cookies for the rest of your life?

Re:Solution:

[Anonymous Coward]

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.

Well for Linux anyway

[al0ha]

A combination of FlashBlock and perhaps RequestPolicy, combined with caching set to 0 and a block on the ever cookie creator domain results in no ever cookies being successfully set on FF 3.6.10 on RHEL 5.4 - I'd venture to guess it will be the same for other OS running FF at least.

If I don't block the domain cookie creation then just a standard cookie is created.

Re:Well for Linux anyway

[Jah-Wren Ryel]

Make the folder ~/.macromedia read only. Works with Linux, but not in Windows.

I just tried it under linux.
When I made the empty ~/.macromedia directory read-only, the flash plugin consistently crashed.
So I made sure that Flash_Player sub-folder was created by the plugin first, deleted any cookie files and then did a recursive chmod -R a-w ~/.macromedia and it seems to work fine now.

Ufortunately

[antifoidulus]

Now that the Cookie Monster has gone all health food we cannot rely on him to help us out here.

Evercookie = Nevercookie

[the_raptor]

With Adblock plus, NoScript and BetterPrivacy Firefox addons I had to whitelist the domain before "Evercookie" would even work. And even then as soon as I revoked permissions for everything except NoScript the only bit that stuck was the cache image "cookie". Considering there are already addons to prevent normal cookies and flash cookies it would take all of a day, after this method for "eternal cookies" appeared in the wild, for an addon to be released that blocked it.

The only message from this and previous articles is "most people are stupid and don't follow basic steps to maintain their security and privacy".

Re:Solution:

[Anonymous Coward]

Don't accept cookies.

No, not a solution. RTFA. It doesn't matter whether you accept cookies or not. The only two methods of protection are (a) use Safari in private browsing mode, and quit and restart the browser between each and every site; or (b) block absolutely all javascript everywhere without any exception ever. Neither of these is really satisfactory.

Plus, these evercookies transfer from one browser to another because they get stored as LSOs.

Why I dont run my browser as me anymore

[DarkOx]

Its reasons like this and others I no longer run my browser under my own user account. I have a separate account I run the browser as, actually two there is one I use just to access my bank, and give it permissions on my X server. It has no group memberships that will let it do anything other than read access to system binaries and libraries, basically its only a member of users. I than give my own user account permission to run the browser as the other user with sudo.

This way I can delete the entire home directory from time to time, or anytime I suspect something fishy has happened.