A disk drive data storage device and a method for implementing a sector selectable write-once read-many (WORM) functionality on the disk drive storage system are disclosed. Data stored in a sector on magnetic storage media or on rewritable optical media are protected from being overwritten by having additional (WORM) bits in the sector header to denote the protection status of the data in that sector. When data is to be written to a sector of a disk drive of the storage system, the sector header for that sector is read and the WORM bits are examined. If the value of the WORM bits indicates that the sector is protected, the write command will not be executed and an appropriate error condition is posted to the host system. If the WORM bits for the sector indicates no WORM protection, the data is written to the sector.