Contrary to popular belief, Valve Anti-Cheat (VAC) still monitors CS 1.6 on Steam. VAC scans loaded modules. If an unknown, unsigned DLL is loaded into hl.exe , the account can be permanently banned from all VAC-secured servers. The ban is not limited to CS 1.6; it affects other GoldSrc games like Counter-Strike: Source and Day of Defeat .
DLL injectors have been part of the CS 1.6 ecosystem for decades. Early developers like Vasily Pupkin cs 1.6 dll injector