eatmore's blog

By eatmore, history, 4 months ago, In English

Looking at the scripts that Codeforces is loading, I found that it is using Evercookie. Evercookie is a script written by Samy Kamkar (the same guy who created Samy worm) which creates "supercookies", pieces of information that a website can store on the user's machine that are intentionally made difficult to get rid of. Supercookies are generally used for tracking, and the use of such technology would be understandable for an anti-privacy company such as Facebook, but why is Codeforces doing this?

 
 
 
 
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4 months ago, # |
  Vote: I like it +360 Vote: I do not like it

We need it to fight with cheaters only. This information can be useful for analyzing dishonest behavior. Every round we have dozens of people trying to break the rules — this helps to identify them. Each round I spend from an hour or more on the analysis of suspicious coincidences in solutions, the first places of troll accounts in div2, and so on. This is a big, though unnoticeable job.

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4 months ago, # |
  Vote: I like it +37 Vote: I do not like it

"anti-privacy company such as Facebook".. LMAO!

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4 months ago, # |
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Btw, how did you catch this thing? "By hand" or there is a tool for that? My ghostery plugin does not see it...

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    4 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    You can see a bunch of evercookies as cookies set on requests to Codeforces.
    You can also see these measures on the login page source.

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4 months ago, # |
  Vote: I like it +24 Vote: I do not like it

Codeforces also uses browser fingerprinting.