1. In a computer system including a host computer, a storage device having a magnetic disk drive, and a fiber channel connection storage controller employing an ANSIX3TT11-standardized fiber channel as an interface between the host computer and the storage device, the magnetic disk drive being operable under control of the fiber connection storage controller, the fiber channel connection storage controller comprising; N_Port_Name information which is information issued from the host computer for distinctly identifying the host computer is preinstalled in the storage control device prior to start-up of the host computer; the storage control device has means for permanently storing therein the information until this information is reset; after startup of the host computer, the host computer generates and issues to the storage control device a frame storing therein N_Port_Name information; the storage control device has means for comparing, upon receipt of this information, the N_Port_Name information distinctly identifying the host computer as already set and stored therein to the N_Port_Name information presently stored in a received frame; and, a fiber channel connection storage control device has means for eliminating unauthorized access from the host computer in a way such that when the comparison results in match, processing based on an instruction of the frame is continued, and when failed to match, a link service reject (LS_RJT) frame for rejection of the received frame is returned to the host computer.