> > On Thu, 2005-07-21 at 10:59 -0400, Robert Snyder wrote:
> > >
> > > >Did you mean Data Life Guard, that comes with their HD's? That
only
> > > >writes zero's to the disk; I gues I could run it a couple of
times. Now,
> > > >will that remove partitions, too?
> >
> > Yes the partitions will be gone but all you are doing is writing
zero's
> > over zero's. more than one pass is useless.
>
> Well, on a very low level (I'm talking you need a clean room and very
> expen$ive equipment to see it), overwriting may change the magnetic
state of
> very small areas near the read/write head. Not enough to matter if
you rely
> on the drive's firmware to read the data, for sure; but if reading
what used
> to be on the drive is _very_ important to you, you can tell what used
to be
> on a drive before it was overwritten by examining the leftover
magnetic
> fringes.
>
> The more times you overwrite the drive with the same data, the smaller
those
> fringes become. They can be more garbled by using different data to
write,
> which is why I suggested multiple passes with /dev/random for those
who have
> a good reason to be paranoid (banks, stockbrokers, virus writers, drug
> dealers, etc.).
>
> --
> -eben
There is a thread on Bugtraq right now about Gutmann's theory
that data can never truly be erased.
- Bob
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