Re: need to wipe a disk

On 2011-12-29, Tim Watts <tw+usenet@xxxxxxxxxx> wrote:
unruh wrote:

On 2011-12-28, The Natural Philosopher <tnp@xxxxxxxxxxxxxxx> wrote:
notbob wrote:
On 2011-12-28, Todd <Todd@xxxxxxxxxxxxxxx> wrote:
I have a disk with personal information on it that I need
to wipe.

There's erase and there's eliminate. Do some research:

http://en.wikipedia.org/wiki/Data_erasure

nb

if you are paranoid take a crusher to it.

Otherwise dd will render an data on it totally inaccessible to anyone
without the ability to strip the drive and read it almost by hand.

And almost certainly not even then. Manufacturers spend huge amounts of
money trying to extract the absolutely maximum data density from the
drives. Any data which survives writing 0 to evey byte is clearly data
which could be harvested to increase the data density on the drive.

http://en.wikipedia.org/wiki/Data_remanence

is worth a look.

Whilst it is acknowledged that overwriting will make it fairly impossible
for mere mortals to recover data, the USA's DoD and NSA require more
stringent destruction methods.

That entry is very old. As I said, IF there really were that kind of
data remaining on the disk, the manufacturers could use it to store more
information on the disk. It is to their advantage to make use of every
last possible bit of information from the disk.

If fact if you had read the Wikipedia page you would have seen the
following paragraphs.

------------------------------------------------------

"Daniel Feenberg, an economist at the private National Bureau of
Economic Research, claims that the chances of overwritten data being
recovered from a modern hard drive amount to "urban legend".[3] He also
points to the "18½ minute gap" Rose Mary Woods created on a tape of
Richard Nixon discussing the Watergate break-in. Erased information in
the gap has not been recovered, and Feenberg claims doing so would be an
easy task compared to recovery of a modern high density digital signal.

As of November 2007, the United States Department of Defense considers
overwriting acceptable for clearing magnetic media within the same
security area/zone, but not as a sanitization method. Only degaussing or
physical destruction is acceptable for the latter.[4]

On the other hand, according to the 2006 NIST Special Publication 800-88
(p. 7): "Studies have shown that most of today?s media can be
effectively cleared by one overwrite" and "for ATA disk drives
manufactured after 2001 (over 15 GB) the terms clearing and purging have
converged."[1] An analysis by Wright et al. of recovery techniques,
including magnetic force microscopy, also concludes that a single wipe
is all that is required for modern drives. They point out that the long
time required for multiple wipes "has created a situation where many
organisations ignore the issue all together ? resulting in data leaks
and loss. "[5]"

--------------------------------------------------------


Hwever, disks are cheap. If you are really really worried, then erase
the disk, and then destroy it. Eg open the drive and heat the platter to
red hot to get above the Curie temperature.




.

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