As AuburnEwaste said, just using regular magnets generally isn't sufficient to prevent recovery of the data on a drive. Now that you guys have made me curious about this, I went and looked at the NIST's "Guidelines for Media Sanitization." (If you want to have a fun Sunday reading that, it's right here: http://csrc.nist.gov/publications/ni...ith-errata.pdf. Actually, it's probably not a bad idea to have a copy of it on hand so you can wave it around whenever a customer gets nervous about their data.) NIST defines 4 levels of "sanitization," from weakest to strongest:
(1) Disposal: You literally just throw the drive away, no data destruction.
(2) Clearing: You make it impossible to retrieve the data using standard tools such as data recovery software. Generally, the best way to do that is just to use a software tool to overwrite the drive. (There's a free program called Eraser that can be used for this, for example.) NIST says a single overwrite is usually enough.
(3) Purging: You make it impossible to retrieve any data even using non-standard, sophisticated recovery techniques and devices. To reach this level, NIST recommends degaussing, in which the disks are exposed to a very strong magnetic field. To satisfy NIST's requirements, you have to use an approved hard-drive degausser (and it looks like those start at $500).
(4) Destroying: In the end, NIST says good old physical destruction of the drive is the best, most foolproof way to prevent unwanted access to its data. This means total destruction, or as NIST puts it, "disintegration, incineration, pulverization, and melting." Which actually is what does finally happen to the scrap from these drives, I guess, right?
OK, if you're not asleep yet from reading this, here's one last detail that I thought was interesting: Almost every ATA/SATA drive manufactured since 2001 has a built-in suicide function called Secure Erase. Running that function completely destroys all the data on the drive and is just as effective as degaussing.
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