In a multiuser or network operating system, the process by which the system validates a user´s logon information. A user´s name and password are compared against an authorized list, and if the system detects a match, access is granted to the extent specified in the permission list for that user.
Depending exclusively on any of methods 1-4 is generally inadequate and multi-token authentication systems are the norm. For example, bank ATM systems use a combination of methods 1 and 2 in the form of passwords (PINs) and bankcards.