Can police trace your ip address even if you use a proxy?

[Edmond]

Edit: Misread it. The answer for Warcraft 3 is maybe, as I am no longer familiar how WC3 does their account record/history for online multiplayer. They can still be caught, especially if they slipped up and supplied their actual email address which they verified which can be traced back to them, or said the incriminating message while not proxy-ing.

I also recommend contacting both your ISP and activision-blizzard about this as their property/service/good name regarding said service is being tarnished.

=== Ignore Below as I misread as WoW ===
Correct me if I'm wrong, but WoW still requires monthly monetary transactions to keep an account active for use. If you have the user/character name of the DOS-er and high suspicion of said user being behind the act (ie: said user boasting about the DOS, which I believe WoW servers record chat), then you should be able to trace it back to the DOS-er (or at least, the payer of the account).

If the suspect supplies info that only the DOS-er would know on a public chat (like WoW server) which has personal info, then they are boned. They might be able to fake a IP, but you can't fake an active credit card/transactions as easily.