Place this into your server.cfg:
Code:
sv_pure 2
sv_consistency 1
sv_pure_kick_clients 1
Install SMAC latest build and edit the config:
Code:
// Enable Anti-Wallhack. This may have high CPU usage on large servers.
// -
// Default: "0"
smac_wallhack "1"
Since L4D2 uses lower amount of players so if you're running a server with more than 8 slots then you shouldn't enable this.
Cheers.