VAC — Valve Anti-Cheat — is one of the oldest anti-cheat systems still in service, and it works quite differently from the kernel anti-cheats that dominate newer games.
A platform-wide system
VAC is built into Steam and protects many games at once. When you play a VAC-secured game, VAC runs in the background looking for cheats. Developers opt their game into VAC rather than shipping a separate client.
Mostly signature-based
VAC's core method is signature scanning: it looks for known cheat code in memory. This makes it effective against established cheats but slower against brand-new ones. Valve also delays some bans deliberately — a "VAC delay" — so cheat developers cannot immediately tell which build was detected.
How a VAC ban propagates
A VAC ban applies to the game group it was earned in. You are blocked from VAC-secured servers for the affected games, and the ban shows publicly on your Steam profile. It does not erase your library — you keep your games — but it permanently marks the account.
Account-bound, not hardware-bound
Here is the key contrast. VAC is fundamentally tied to the Steam account, not to a hardware fingerprint. A VAC ban does not, by itself, blacklist your PC the way a kernel anti-cheat's hardware ban does. Some individual games on Steam add their own developer-issued bans on top — and those may use hardware identifiers — but VAC itself is an account-level system.
The takeaway
VAC is the quiet, platform-wide layer: signature-based, account-bound, permanent. Knowing it is account-level — unlike a kernel anti-cheat's hardware ban — is the single most useful fact about how a VAC ban actually behaves.