How does COD detect cheats?

Can you explain, in a concise manner, the methodology employed by COD, or Call of Duty, to identify and combat cheating within its multiplayer environment? Are there specific algorithms or systems in place that monitor player behavior and flag suspicious activity? How does the game's anti-cheat system differentiate between legitimate skill and unfair advantages gained through cheating? Furthermore, what steps does COD take once a cheat has been detected, to ensure the integrity of the game and the experience for honest players?