"VAC" is a catch-all term for all of Valve's anti-cheating mechanisms.

The primary one is a standard user-mode software module, that does traditional scanning.

The AI mechanism you're referring to is these days referred to as "VAC Live" (previously, VACNet). The primary game it is deployed on is Counter-Strike 2. From what we understand, it is a very game-dependent stack, so it is not universally deploy-able.