A method of operation of a self-locking mass storage system includes: providing storage media and an inactivity timer; timing a period of read/write inactivity of the storage media using the inactivity timer; comparing the period of read/write inactivity against a preset maximum idle time; locking access to the storage media when the period of read/write inactivity exceeds the preset maximum idle time; and, resetting the period of read/write inactivity following read/write activity while the self-locking mass-storage system is in an unlocked state.