Passes 5-7: Overwrite the data with DOD 5220.22-M (E) standard.Pass 4: Overwrites the data with pseudo-random values, DOD 5220.22-M (ECE) standard.Passes 1-3: Overwrite data with DOD 5220.22-M (E) Standard.Overwrites a pseudo-random value and verifies the overwrite Overwrites the compliment of Pass 1 (i.e., Zero) Then there are other versions of DOD 5220.22-M that are often used for wiping confidential files from a hard drive or other storage devices that stipulate the use of up to seven passes. According to the US Department of Defense, a hard drive should be overwritten at least three times.

Overwriting data many times makes it unrecoverable and keeps the drive usable. “ĭisk density is also a factor.The DOD 5220.22-M of the US Department of Defense (DOD) is a data erasure standard that states that data on a hard drive or any storage drive should be overwritten multiple times for proper sanitization of the data.

This was true in 1996, and is still true now. As the paper says, “ A good scrubbing with random data will do about as well as can be expected“. For any modern PRML/EPRML drive, a few passes of random scrubbing is the best you can do. If you’re using a drive which uses encoding technology X, you only need to perform the passes specific to X, and you never need to perform all 35 passes. “In the time since this paper was published, some people have treated the 35-pass overwrite technique described in it more as a kind of voodoo incantation to banish evil spirits than the result of a technical analysis of drive encoding techniques… In fact performing the full 35-pass overwrite is pointless for any drive since it targets a blend of scenarios involving all types of (normally-used) encoding technology, which covers everything back to 30+-year-old MFM methods (if you don’t understand that statement, re-read the paper).

Dod data wipe