Attack units, or attack computers, were specialized computers used by the Eminians and Vendikans in the interplanetary war that existed between their two planets, Eminiar VII and Vendikar. On the former planet, these machines were placed within the Eminian war room, in the Division of Control.
There were two attack units, one used for defense and the other for calculating casualties. They were connected to their counterparts on the other planet by a subspace transmission unit.
These attack units were activated in order to launch an immediate counter attack during the Eminiar-Vendikar War. When Spock observed this procedure, while held in the war room on Eminiar VII in 2267, he determined that their war was fought totally with computers. (TOS: "A Taste of Armageddon")