To provide an authentication program and system that can exclude use by unauthorized users even upon the theft of authentication information and the theft of apparatus after authentication.

The authentication system has a prohibition information storage means for storing prohibition information representing prohibited operation content, an input monitoring means for monitoring input operations to a computer when the operation status of the computer is shifted to a usable state, an input information acquisition means for, when any input operation is detected, acquiring input information representing the content of the input operation, a comparison means for comparing the input information with the prohibition information, an authentication means for performing authentication according to the result of the comparison means, and a use control means for shifting the operation status of the personal computer to a use-restricted state if the user authentication fails.

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