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How To Really And Fully Wipe A Hard Drive?
root_dev_X ventures: "Admittedly, this is a random question, but here goes - Does anyone out there know of any ways to totally erase the data on a drive? Some friends of mine got into a discussion about this not too long ago; one of them told me they had heard from a friend in the military that they hooked up old HDDs to modified stun-guns and zapped them in order to totally erase them - apparently this method scrambled the magnetic field of the disk, leaving the data irrecoverable. Does this work? Are there any other methods for "data-destruction" (keeping the platter intact, that is)?" A nice "obliberate data to the point of senselessness" tool would be nice -- or is keeping the platter intact a senseless question if you want true security?
See Peter Gutmann's Usenix paper on secure deletion of data from magnetic and solid state memory for some truly impressive data recovery methods.
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Forward, retransmit, or republish anything I say here. Just don't misquote me.
...and ineffective.
/. needs a new moderation category "didn't get the joke".
I have discovered a truly marvelous sig, unfortunately the sig limit is too small to contain i
Put it under that gun that shrinks quarters. Give it to a friend. Say "Hey man I compressed my hard drive" :)
Give it to a five year old. They can destoy anything .
Never play leapfrog with a unicorn. Or a juggernaut.
All of you who said that no matter what, data can't be erased, gave me an idea.
:) Even more interesting is that the files you use the least may eventually become unrecoverable and forgotten over years, lessening the need to clear out your clutter. Files that you haven't used in a while might take a bit of time to come up, but you usually won't mind the wait. Stuff you use all the time will always be available. So how about it, kernel hackers? And my sig's appropriate this time around, too!
Unlimited storage.
That's right. Every time you need more disk space, simply delete something not used in a while, then overwrite it with a new file. Need that old file back? Great - have the filesystem automagically run a recovery on it. Put it into the kernel, and we've got blackholefs.
The end result is a bottomless pit of unlimited drive space
(and yes, I am joking, but if someone can think of a way to really do this them I'll REALLY be impressed!)
You can accomplish anything you set your mind to. The impossible just takes a little longer.
Lawrance Livermore used to take decommissioned hard drives and Syquest style media in the green area and dump the platters into a vat of acid. Floppy disks went through the three-pass shredders, so you end up with fine magnetic dust.
The original specification for overwriting disks containing classified but not secret data called for 300 overwrite passes, alternating between all-zeros, all-ones, alternating zero-one, alternating one-zero, and "worst case pattern" (for those old MFM drives, the 16-bit pattern 0xDAC3). You needed to know the exact drive geometry, because you want to do all the tracks on a platter individually, using a back-and-forth sweep so as to get into the guard bands as much as possible.
(In other words, wipe from cylinder 0-max on head zero, then from cylinder max-0, then go to the next pattern and wipe. Then you go to the next head.)
Is it worth it? At today's prices, I don't think so.
GNU fileutils has a program called 'shred' that writes over a harddrive ~30 times in a way that makes data recovery ~impossible. I have two drives in my Linux box. What I do is mount the one I want to wipe out as ext2. Then
/dev/hd[a,b,c or d]
shred -z
It takes ~6-8 hours to wipe out a 10GB drive.
- The naieve way
- The cryptographic way
- Overwrite all your data with 0xFF.
- Overwrite all your data again with 0x00.
- Overwrite all your data with a good random or pseudorandom stream of data.
- Repeat this process at least seven times--more if you like.
- The smart way
... All this may sound overly paranoid, but if your data really is that important it's the only way to go. A new hard drive is $250 nowadays; the cost of important secrets getting out is easily a few orders of magnitude higher. Physical destruction of media is the only way to be fairly certain that the data is destroyed.Delete your files. This will keep a six-year-old from recovering them. If you're running a UNIX which doesn't have a recycling bin, nor a broken file system which still leaves data lingering intact long after "deletion", then you'll be able to keep a seven-year-old from recovering them.
Follow the following procedure:
Follow the cryptographic method outlined above. Then get out a sledgehammer and physically destroy the drive. Drop the platter in a metal wastebasket, douse it in lighter fluid and set the thing on fire. Don't stop until the platter is totally destroyed.
Keep in mind that the cryptographic method may fail, and even a bulk degausser isn't guaranteed. They can do amazing things with electron microscopy today.