Re: Cant find an 'answer' no matter where I look or post



On Fri, 15 Sep 2006, in the Usenet newsgroup alt.computer.security, in article
<0e2mg2thd7go3f7tdo8saatf7n5npfkhtv@xxxxxxx>, Inquirer wrote:

On Fri, 15 Sep 2006 14:33:41 +0100, JB wrote:

Security Services have a three or four level deletion process the last
of which entails reducing the actual drive to a fine metallic powder.

Do you have a citation for that?

Why do they bother with the first two or three then?

Start with the paper of Peter Gutmann of the University of Auckland from
1996, (http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html) even
though it's quite dated now.

Then look at the paper by Gordon F. Hughes of the UC San Diego Center for
Magnetic Recording Research in October 2004
(http://cmrr.ucsd.edu/hughes/CmrrSecureEraseProtocols.pdf) which notes
that in 2004, a disk fragment that contains a single 512-byte record block
in size (about 1/125" or 0.20 mm) can be read in about an hour. Given the
then common disk size of (perhaps) 10 Gigabytes, the problem of finding the
"right" disk block (or disk fragment) becomes apparent.

Then look at the NISPOM (DoD 5220.22M), and see what it _requires_ for
the "sanitizing" of media that held (officially) classified material. Up
to (US) Secret, it's just a triple wipe (ones, zeros, random). Above that,
it's (basically) to slag the media. The idea is to first destroy the
magnetic media (either by using an extremely strong magnet, or raising
the temperature of the media above the Curie temperature for a long
enough period in hours to demagnetize it), and then to make sure of the
results, melting/dissolving the remains (which involves much higher
temperatures or down-right dangerous chemicals). The residue is then
buried in a secure land-fill, but I'm not sure this isn't a requirement
of the results of the dangerous materials used.

The average home user is rarely able to find a magnet of the required
strength (we're well into the 8-10,000 Oersted range now - several orders
of magnitude more than that refrigerator magnet produces), and the Curie
temperatures are generally in excess of what mummy's oven is capable of.
Finding and actually obtaining suitable chemicals is rather difficult,
never mind the hazards of using them and disposing of the results.

Thus, you're stuck with sanding the media off the platters (use 600 or
"Ultra Fine" silicon carbide grit), or chucking the platters in a drill
press (using a large bolt and nut) and using a fine file to grind the
platter to a powder with a grain size less than 0.001 inch or 0.025 mm.
Not entirely practical, and you should wear a breathing (dust) mask and
safety glasses for either method.

The fairly common urban legend cited by posers everywhere is to stick the
drive (or even just the platters themselves) in a microwave oven. While the
sparks may look impressive, this causes far more damage to the microwave
oven than to the disk drive or platters. The similar idea of passing it
through the metal detector or X-ray machines at the airport is equally
useless.

But then, if you are in England, all this is unnecessary. A recent post to
the Usenet newsgroup "alt.humor.best-of-usenet" (the original posting was
to "uk.misc") has a cheap and perfect solution:

-----
What's the best way of disposing of them in such a way that the hard
disks can never be used again, not even if they swap parts with 'donor'
hard disks?

Post them to yourself via City Link to destroy them, and then post
them again via Parcel Force for disposal.
-----

Look it up if you don't know the two organizations.

Old guy
.



Relevant Pages

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  • Re: Why magnetic drums was/are worse than disks ?
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