Patent ID: 7975289

Claim:
A computer-readable non-transitory medium, storing a program causing a server machine to execute: a registration step which registers a first authentication information of a user and a first MAC address; an authentication request receiving step which receives, from a client machine, an authentication request including a second authentication information, a second MAC address, and address change information as to whether or not an original MAC address of the client machine has been changed to the second MAC address; and an authentication responding step which, upon determining the second authentication information and the second MAC address are in agreement with the first authentication information and the first MAC address: if non-change in the second MAC address is recognized from said address change information, issuing an access permit in response to the authentication request from the client machine, and if a change in the second MAC address is recognized from said address change information, informing a system manager of the change in the second MAC address, and issuing an access permit or an access refusal in accordance with an instruction of the system manager to the client machine.