"Reflecting its original requirements, the DoD 5220.22-M data sanitization method, or the DoD 3-pass method, is usually implemented in the following way:
- Pass 1: Overwrite all addressable locations with binary zeroes.
- Pass 2: Overwrite all addressable locations with binary ones (the compliment of the above).
- Pass 3: Overwrite all addressable locations with a random bit pattern
- Verify the final overwrite pass.
Erasing an HDD using the DoD 5220.22-M data sanitization method will prevent all software-based file recovery methods, as well as hardware-based recovery methods, from recovering meaningful data from the drive."