Abstract: A computer security system protects the computer software from unauthorized access and the computer hardware from unauthorized intrusion. At the start up of the computer system, the computer's keyboard and diskette drive are disabled. The user is required to identify himself through the use of a non-keyboard device such as a magnetic card reader. As a means of further validation, the user enters a PIN via the keyboard which has now been restored to function. A valid user will be allowed access to those programs for which he has been preauthorized. Attempts to gain access to the operating system or to programs for which the user is not authorized will be filtered by the security system to prevent unauthorized access to certain programs or to preclude efforts to thwart the security system. An alarm circuit provides security to the computer hardware.