How does a 7- or 35-pass erase work? Why would one use these methods?

stalepretzel picture stalepretzel · Nov 10, 2008 · Viewed 52.9k times · Source

How and why do 7- and 35-pass erases work? Shouldn't a simple rewrite with all zeroes be enough?

Answer

epochwolf picture epochwolf · Nov 10, 2008

A single pass with zeros doesn't completely erase magnetic artifacts from a disk. It's still possible to recover the data from the drive. A 7-pass erasure using random data will do a pretty complete job to prevent reconstruction of the data on the drive.

Wikipedia has a number of different articles relating to this topic.

http://en.wikipedia.org/wiki/Data_remanence

http://en.wikipedia.org/wiki/Computer_forensics

http://en.wikipedia.org/wiki/Data_erasure