FairFight is analitical anti cheat system, it is analyzing players movements and trying to predict anomalies that shouldn't happen. For example you are shooting at somebody, then this system compares your data with server and tries to predict if it was possible to shoot at that player. Are you not using any hacks, like shooting through walls or constantly headshoting players through smoke. Stuff that for normal players wouldn't be possible to do. Yesterday night there was lots of fairfight bans. Almost all chat history was full of them.