An access controller for peer-to-peer communication networks which monitors the data packets transmitted between stations, determines when an access that needs to be controlled is being made, and then either destroys the packet or transmits one or more packets which appear as legitimate message packets to the stations but which, in fact, terminates or alters the communication path between the two stations. Since the invention is free of any particular protocol restrictions, it can be implemented with any type of protocol and at any layer of that protocol. And since the access control mechanism is neither part of the physical communication path nor part of the communication primitives, the stations cannot detect, in any direct sense, that their access is being controlled, and they do not need to be programmed to follow any special control protocols, or to use encryption. A signature signal can be used as a safety mechanism to prevent multiple access controllers from controlling the same network, to prevent an unauthorized access controller from seizing control of the network.