if I'm not mistaken it's not completely clean unless it's destroyed, and even then it's still possible to get information from it provided you have the means. your midget amputee porn is still going to be on there.
Yes, destroying is the preferred method, but a handful of contractors make wipe tools that are to DOD specs. You HAVE to destroy a drive that contained anything secret class or above, but for unclass they will use the wipe tool.
Long Security Wipe - Overwrites data six times using four different data patterns.
Long Security Wipe with Format - Overwrites data six times using four different data patterns, then performs a factory style low level format.
EXCEEDS SECURITY REQUIREMENTS FOR DEPARTMENT OF DEFENSE - With EraserDisk, once the information is gone, there’s no way somebody can get it back. The only method more safe would be to physically dismantle the drive and destroy the platters inside.
I don't know what method they use overwrite the data but I'm sure it's not just writing zeros.
I've read if you use tools that write 1's or 0's in blocks larger than the regular block sizes effectively sanitize the disk. however as always, I'm sure there is SOME way to recover the data. and I'm sure other people on here know more about this than i do.