Hacker is a game mode cut from Call of Duty: Black Ops II that was playable in the beta. It is unknown why it was removed from the retail game.
As the name suggests, it was a point-based free-for-all type mode focused around hacking neutral A.G.R.s. A.G.R.s could be temporarily disabled in order to hack them. Points were given for hacking, killing other players, and getting kills with the A.G.R.s. Kills with the A.G.R. provided a higher score than if the player had killed enemies themselves.