A security system for a network connected with a plurality of computers is disclosed, in which one of the computers monitors the internal status thereof. An internal status monitor unit of the one computer detects the occurrence of a fault and the type of the fault in the one computer. An access control unit of the one computer controls the access to the resources of the one computer. An information transmission unit of the one computer transmits a message to other computers of the network indicating the occurrence of a fault and the type of the fault in the one computer through the network in the case where the internal status monitor unit detects the occurrence of the fault in the one computer. The access control unit executes the processing for protecting the resources of the one computer in accordance with the type of the fault of the one computer in the case where the internal status monitor unit detects the fault of the one computer.