A lock assembly for retaining computer peripheral devices in a housing. The lock assembly includes a spring-loaded lock bar that is movable between an unlock and a lock position. The lock bar is secured in the lock position by engaging a lock pin in one end of the lock bar. The lock pin is coupled for linear movement to a rotateable lock cylinder. A key is used to rotate the lock cylinder between lock and unlock positions. The key may be removed and stored in a secure place after locking the lock assembly to prevent unauthorized removal of peripheral devices from the housing. Brackets are mounted on opposing sides of the housing to retain the lock bar and to provide guide slots for controlling movement of the lock bar between lock and unlock positions.