Cheating

Counter killer has been a prime target for exploitation by cheaters since its release. In-game, cheating is often referred to as "hacking" in reference to programs or "hacks" executed by the user.
Wallhacks allows players to see through walls. These work by displaying objects that are normally obscured or by replacing opaque game textures with translucent ones. As the engine only renders the immediate area around the player, this does not allow a player to see the entire level at once.
Speedhacks give the player increased foot speed. These work by sending false synchronization data to the server.
Recoil hack removes any recoil (and thus improves accuracy) from a player's firearm.
No spread is used to remove the random deviation normally experienced when the player shoots. This is similar to the recoil hack.
Aimbots help the player aim at enemies. Practically the same as auto-targeting, These work by either modifying a bullet's in-flight path, or automatically moving the player's crosshair onto an enemy.
ESP shows textual information about the enemy; such as health, name and distance; also information about weapons lying around the map, which could be missed without the hack. Most ESP cheats show info through walls.
Barrel hack depicts an enemy's gaze as a visible line.
Anti-flash and anti-smoke remove the effects of the flashbang and smoke grenade. Implementation is derived from the wall hack.