Valve on Cheating
Unfortunately, I can't give out more information. We're aware of the current problem with cheating and are working to find a solution. We play on-line and are just as frustrated by cheaters as you are. We're working to implement a long-term solution, and coding for that has already begun. This will involve many phases of attack. I'm sure you understand why I can't give out the specific details of our strategy. However, it WILL NOT be "a year or so" before we start releasing cheat-prevention code. We'll be phasing it in during future updates.
From The Chatty
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Cheater pants!