[K12OSN] OT: hard drives and magnets

Steven Santos steven at simplycircus.com
Fri Mar 16 17:11:13 UTC 2007

It is possible to wipe a hard drive with a magnet.  The catch is that it
must get through the sheilding of the PPC case, and of the drive itself.
That means that it has to be an extremely powerful magnet.  It also helps
greatly if the magnets field is tuned to better do that job, kind of like
you have with some of the magnetic door barriers that are designed to wipe
any media going out of a secured environment.

Now, again, while its possible to do, its really hard.  Even if you open a
HD case itself and get the magnet spinning and very close to the platters,
your still going to need and industrial power electromagnet to do it.

I remember back in the 386 days a product that looked like a standard
floppy, but when put in a drive and spun up, emitted a VERY powerful
magnetic field which would unrecoverable wipe any hard drive in the case.  I
think they still make them.

As to leaving the drive formatted, no way.  A magnet would wipe those bits
just as quickly as it would wipe data bits.  A magnet does not have the kind
of control over what it wipes to do this (at least not without all of those
control circuits).


Steven Santos
Director, Simply Circus, Inc.
Email: Steven at SimplyCircus.com
 Mail: 14 Pierrepont Road
       Newton, MA 02462
Phone: 617-527-0667
  Web: www.SimplyCircus.com <http://www.SimplyCircus.com>

> -----Original Message-----
> From: k12osn-bounces at redhat.com [mailto:k12osn-bounces at redhat.com]On
> Behalf Of Eric Brown
> Sent: Friday, March 16, 2007 12:33 PM
> To: K12OSN at redhat.com
> Subject: [K12OSN] OT: hard drives and magnets
> Hello all,
> A student has been using a school owned Acer laptop w/xp pro, less
> than 6 months old.  It was brought to me today saying NTLDR could not
> be found.  In my expirence, this means it's either booting from a
> non-bootable disk, the hard drive is damaged, or at least a major
> chunk of the hard drive has been erased.  Using some of the various
> recovery Linux live cd's, I determined that the hard drive is healthy,
> and is totally empty, save for an empty "Recycle Bin" folder.
> The kid claims they may have put a magnet near the computer.  The
> principal claims certain types of batteries could wipe a hard drive.
> What reading I've done says a magnet may corrupt some files on a hard
> drive, but it would take an industrial size magnet to wipe it and it
> would also be rendered unusuable in the process.
> Has anyone gone through this?  Is it possible to wipe an entire hard
> drive with a magnet found at home, but still have it usable?
> I'm currently running a recovery (unformatting) program on the disk so
> I can see what the browser history and such were before the culling of
> the drive.  The reason I want to make sure I'm on firm ground here is
> that the student's mother is very difficult to deal with, and believes
> anything her child tells her, unless there were 20 witnesses and a
> video of any transgression.
> Thanks,
> Eric
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