An access control system and an access control server using Terminal Services or the like, which prevents information from being leaked are provided. The access control system includes one or more computer units, one or more terminals, and the access control server that controls a hub. The one or more terminals are coupled with the one or more computer units through a network and the hub. The hub controls access from the one or more terminals to the one or more computer units. In accordance with the result of the authentication, the access control server authenticates a user who operates one of the terminals and sets the hub so that a network link for a particular protocol is established between the terminal operated by the user and a particular one of the computer units.