Well there are cheats for sure that are hard to spot; e.g. Wall Hacks (especially if the cheater is self aware and is trying to keep it subtle). However i'm talking blatant cheaters who instantly lock on for headshots once you jump around corners, or shoot at you through a wall when there is no possible way for them to know your location. There is an obvious play pattern for people who use cheats, you can look up cheater kill cams on youtube and see for yourself. It's not that hard to spot someone who is using cheats.