How does Valve Anti-Cheat (VAC) work?

Many Source engine games are run on servers that are “VAC-Secured”. How does the VAC really work? What is it looking for? If it finds something “bad”, what does it do?

Is there any way a user can appeal a VAC ban?


From the Steam KB:


All VAC bans are permanent – Valve has a zero-tolerance policy for cheating and will not lift VAC bans under any circumstances.


Any third-party modification to a game designed to give one player an advantage over another is classified as a cheat or hack and will trigger a VAC ban. This includes modifications to a game’s core executable files and dynamic link libraries.


The following will not trigger a VAC ban:

  • Using chat programs like X-Fire
  • Playing multi-player mods which do
    not modify core .EXE and .DLL files
  • System hardware configurations
  • Updated system drivers, such as video
    card drivers
  • Using custom skins, sounds or map

So if your mod fall into second category but not first, you should be okay 🙂

It might also be good to know that VAC bans don’t happen instantly, usually a random time between a week – 2 months you will see this ban occur. This is to help stop the cheaters from knowing which hacks actually get pass VAC Security.

Source : Link , Question Author : Jeffrey , Answer Author : Nick T

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