You probably have a few old hard drives sitting around collecting dust. They may not be MFM or RLL drives, but you’ve probably got some 8 or 20 gig drives sitting around from an old upgrade. Do you even remember what OS was on those systems, let alone what sort of sensetive information might be sitting on those drives? According to some of the latest findings out there, you better either take the time to do a military-grade wipe on the drives or physically destroy them; the alternative is throwing them out and hoping no one comes along and does a forensics analysis of your old drive in the hopes of finding your credit card information.
Deleting the files on your drive just isn’t enough anymore. The tools exist for even an amateur computer sleuth to recover files on the hard drive if it wasn’t properly formated. And we need these tools for the occasional mistake or disaster, but we have to be aware of the fact that the bad guys have them too. Anything you might be able to recover using testdisk or ddrescue will also be recoverable by someone snooping for account information or credit card numbers.
So here’s what I do: at work I use any of the many Linux LiveCD’s, as long as they contain Wipe. Three or four passes over the data with random 1’s and 0’s make the data pretty hard for anyone except the most talented and dedicated forensics analyst to recover any data. And at home I have even a simpler solution: a cordless drill with a 3/8″ titanium bit. One or two holes in the platter make certain anyone without a scanning electron microscope isn’t going to be able to use the disk in the future. And it only takes about 30 seconds per drive.