Plus they will just pull data from the edge of the track if you don't use the Secure Erase firmware that lets you put the head slightly off track edit: Said it was debated if single pass was enough, but it seems there has been some definitive forensic research done on this that has essentially officially determined that one pass is enough. Last time I did much research on this, there were people in the forensics community who argued both ways. Now I can find test results that show who was correct . I guess it is note worthy that the department of defense still does not consider data wipes to be enough to sanitize a drive, requiring complete degaussing and physical destruction.