Valve Anti-Cheat, abbreviated as VAC, is an anti-cheat solution developed by Valve Corporation as a component of the Steam game development platform. Those who are VAC Banned cannot enter a VAC-enabled server, However, this only applies to the engine the game uses. For example, if you are banned on Counter-Strike or Half-Life, only games which use the Goldsource engine will be affected. You can still play games and connect to secure servers on games that do not use the same engine.