I posted recently on how to remove/destroy the data on a hard drive so no one can recover it. Data remanence discusses the physical properties of storage devices that determine what must be done to completely clean the data from a device you intend to discard, sell, or give away.
I’m sure this will be interesting or useful to at least a few of you. I helped someone clean her Macbook hard disk prior to selling the laptop recently and this article would have come in handy then to help her understand the processes we used and why they work.
I agree with the author of this G+ post that the easiest, most foolproof (and therefore best) method of destroying the data on a hard disk is to destroy the disk itself. Anyone in doubt should just destroy the drive.
Failure to destroy the data on a hard drive can result in profoundly embarrassing or costly consequences, as noted in these two items:
Strictly speaking, it’s not necessary to destroy a drive to remove sensitive user data. Those interested in the technical factors behind this can read this article and the linked source material: