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

On Fri, 15 Sep 2006, in the Usenet newsgroup, 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, ( 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
( 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

But then, if you are in England, all this is unnecessary. A recent post to
the Usenet newsgroup "" (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

  • Re: hd troubles?
    ... >>something (besides a big ass magnet) for functionally ... Since it's the holiday season: ... -Take the disk apart and use the platters as Christmas tree ornaments or ... -If you live somewhere warm, use the platters as drink ...
  • Re: what motion? what velocity?
    ... |> In the configurations Mr. Faraday used, yes, the slide contacts are needed. ... with the magnet) configuration would have a contact with a moving body to ... Orient it so that this motion is perpendicular to both the field lines (that ... |> |>Consider the magnetic disk with poles on the flat sides. ...
  • Re: Deleting data from a HP 3000 disk drives
    ... >> Purging information is a media sanitization process that protects ... > Unless your ATA disk has a firmware secure wipe function, ... > sight of everything but the drives firmware, ...
  • Re: Electrons magnetic field: A point of confusion
    ... If you first assume that a charged spinning disk, or even an electron, ... magnetic field, but will not behave as a magnet when in the field of ... because they are bound within systems of charges. ...
  • Re: Why magnetic drums was/are worse than disks ?
    ... I already told you that the maximum number of disk platters isn't decreasing much at all. ... There's nothing about thermal expansion that would 'encourage' reductions in platter count: some desktop drives are being made with fewer platters (and heads) so that they can be manufactured more cheaply - in fact, some drives have been made that use only one side of one platter. ... Split the difference to make a round number, and say that the multi-head assembly length can vary with respect to the 'pencil' length no more than +/- 0.000001 inch, at least if you want track density comparable to a contemporary disk's. ...