При коненкте на сервер с установленным VAC (Valve's anti-cheat system) вам выдастся вот такое интересное сообщение:

You are joining a server that implements Valve's anti-cheat system (VAC). Please note that the use of Cheats is a violation of your End User License Agreement for the software and/or your Steam Subscriber Agreement.
If Valve or the game host detects your use of Cheats on an VAC-enabled server, your Steam Subscription and/or your product key for the software will be banned from playing on VAC-enabled servers for one (1) year.