On Wed, 2004-09-08 at 17:10, Thomas C. Greene wrote: > I've created a few simple shell scripts that use /dev/urandom to wipe data > from the swap partition, wipe unused disk space on the root partition, or > wipe an entire disk. You'll find them at http://basicsec.org/tools.html. While I think it's very useful to use a random source of data, you might also want to try using 'aespipe' from the loop-aes package (http://loop-aes.sf.net). You can pipe /dev/zero at aespipe. With random keys you have a much faster source of data to fill the device. Change the key each overwrite and overwrite a number of times. > Data hygiene is generally easier on *nix because there are fewer hiding > places > than on a Windows system, but there are no free wipe tools that i'm aware of. > > So I got busy. It only seems easier. But the data isn't gone per se. > > This is not a perfect solution, but it's a step. I'd be delighted to knows > from fellow list members what I might do to improve them. The scripts are > freely available and freely modifyable (is "modifyable" a legitimate word?) I suggest at the very least, multiple overwrites. A single overwrite isn't going to erase the data in an unrecoverable manner. It's better than just rm'ing the file, but it's still recoverable. It really depends on the threat you are worried about. If it's your kid sister, a simple 'rm -rf' might do. If it's a place where you're selling your hard drive on ebay, you might want to wipe the entire drive*. If you're worried that the FBI is going to kick down your door (and you haven't been served just yet), you want to wipe the drive many times over. Then open it, sand it down and put it in the microwave for effect :-) Magnetic force microscopy is a threat that is very real for many people. It would be of great help for you to read this paper: http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html You could also tell users to start off with proper disk encryption in the first place. It doesn't matter as much about wiping a disk when all of the data is encrypted. We can all dream, can't we? If you are really interested, I suggest you also pick up a copy of "Computer Forensics" by Kruse and Heiser. * for the record I would not sell my hard drive on ebay with one wipe or even with many. I know I have bought a few drives just to practice my recovery skills, I am sure others do this as well. -- Jake Appelbaum <jacob@xxxxxxxxxxxxx>
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