I worked in a decom department for a while, wiping hard drives... but I never knew the difference between a single pass wipe, or a 3 or 7 pass one. I know the disk is written multiple times to ensure that all the data is gone, but what's the point in more than one pass? Surely if a drive has been completely written with 00's, nothing is recoverable... what are the benefits of doing this multiple times?
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Anonymous2006-02-21 12:48
No, there is a certain degree of residual magnetic flux even after the entire disk has been overwritten with 0s, 1s or even randomly, which means data can be recovered with the right software/know-how. Ever had a cassette tape where you recorded over something, but can still faintly hear the old recording during the silent parts? This is much the same thing (only digital data, not analogue). Multiple passes weaken the "residue" until eventually it's virtually indecipherable.