Erasing data on a "dead" drive

On Jul 13, 2006, at 5:23 PM, Edward Reid wrote:

> Of course, this assumes that bulk erasing really worked ... I
> don't recall anyone ever checking the results! Perhaps it was all
> psychosomatic. ;-)

I went so far as noting that a cassette bulk eraser took a tape set
up in a program's expected format and made it not be in that format.
I never "developed" a sample to see whether readable bits were still
there. (Bits were big in those days, and easy to see after spraying
with magic potion and using magic light--the process didn't take much
magnification).

   --John

On Jul 14, 2006, at 7:43 AM, David Ross wrote:

> I did get one crashed platter out of it. Useful to show people what
> happens.

The world needs more trivets. Unfortunately, the modern drives only
supply material for mini-trivets, for which there is little use.

   --John (remembering the good old days)

On Jul 14, 2006, at 7:43 AM, Geoffrey Odhner wrote:

> This allows the military to finally have
> a fast way to erase sensitive data in a short timeframe when a
> vehicle carrying it is disabled in vulnerable territory.

 From one of the Army Field Manuals back in my day: all troops "must
be trained to destroy the equipment issued to them."

   --John

Yes, I can assure you a bulk tape eraser works fine on my old 10 inch reel to reel audio tapes. You just fire it up close and pull it away. If you really want a static gorilla permanent magnet that will almost pull nails out of the wall, extract a magnetron magnet from an old microwave. And stand back. Keep it far away from anything digital.

JAM

On 14 Jul 2006, at 08:43 , Geoffrey Odhner wrote:
> Georgia Tech Research Institute has just recently announced a new
> technology that finally allows them to erase disk drives with
> external permanent magnets. This allows the military to finally have
> a fast way to erase sensitive data in a short timeframe when a
> vehicle carrying it is disabled in vulnerable territory. The
> previous technologies were quite time consuming, because, for one
> thing, most permanent magnets simply don't have a strong enough field
> to accomplish this task through the range necessary to thoroughly
> erase the data on a hard drive. This new mini-fridge-sized device
> has a magnetic field comparable in strength to an MRI machine, and
> can erase an entire hard drive or other magnetic media in a few
> seconds. Your donut magnet might erase parts of the hard drive, but
> it won't reliable protect the data from being recovered.

When I have data on my drives that I think the NSA might be willing
to invest a few hundred man-hours into recovering, THEN I might worry
that my doughnut magnet is not up to the task. As it is, a few
minutes renders drives with some problems, but bootable, completely
unusable. When I sent a 20GB drive back that was making clicking
noises (This was several years ago when a 20GB drive was not a
paperweight) I tried to recover data off of it after I gave it my
magnet treatment and was unable to recover anything at all using 7 or
8 different disk recovery tools, including on linux based boot disk
that, I believe, tired to use dd to copy the drive image and then
tried to parse through for any useable data streams.

Good enough for my non-military grade data, and unless you're working
on Defense contracts, probably good enough for you.


--
Eyes the shady night has shut/Cannot see the record cut
And silence sounds no worse than cheers/After earth has stopped the
ears.

On 13 Jul 2006, at 18:23 , Paul Atroshenko wrote:
> (I say "allegedly" because we Aussies still maintain the notion of a
> presumption of innocence... and it is also possible that the offending
> material found its way to his laptop without the Prosecutor's
> knowledlge.)

More than just possible if it's a windows machine. Many of the
viruses out there are specifically designed yo turn your machine into
a porn server...

--
"There's sex and death and human grime in monochrome for one thin
dime, and at least the trains all run on time but they don't go
anywhere."

johnamoodydc wrote:
> Yes, I can assure you a bulk tape eraser works fine on my old 10 inch
> reel to reel audio tapes. You just fire it up close and pull it
> away. If you really want a static gorilla permanent magnet that will
> almost pull nails out of the wall, extract a magnetron magnet from an
> old microwave. And stand back. Keep it far away from anything digital.

Better yet, the head magnets from old 3380 disk drives. These things are
about the size of soccer balls and will distort displays from about 5'
away. CRTs that is.

For those who don't know, a 3380 is a disk drive from the 80s used by
IBM main frame setups. It was the size of a large side by side fridge.
Platters were 13", maybe bigger. Heads were dual and from each side.
This thing had motors bigger than most HVAC units. :)

On Jul 14, 2006, at 10:26 AM, Google Kreme wrote:

> When I have data on my drives that I think the NSA might be willing
> to invest a few hundred man-hours into recovering, THEN I might worry
> that my doughnut magnet is not up to the task.

Note that my IBM laptop's original drive failed seemingly by breaking
some part of the head assembly. It makes a satisfying rattling sound
to this day. I keep meaning to find the time to drill into it and
look at what actually happened.

So your magnet *might* be damaging the heads rather than the data.
Or both, or just data.

   --John

At 7:28 AM -0700 7/13/06, Google Kreme wrote:
>I have a large magnet. Being paranoid, whenever I send a dead drive
>back to maxtor, which I do once or twice a year... grmbl... I simply
>set the drive upside down on it for a few minutes, wave it around a
>couple of times, and drop it in the box.
>
>(It's a large donut magnet about 12cm across and is quite hard to
>pull off the fridge when I need it. No idea where I got it, lo
>those many years ago)
>
>
>[Long ago, a friend extracted the powerful magnet from a toner
>cartridge. It was a long rod, and it was strong enough to make it
>difficult to remove from a metal-backed blackboard. We tried to use
>it to erase SyQuest cartridges and floppies, and amazingly, never
>managed to hurt either. So... no telling if this will work or not.
>-Adam]

We tend to overestimate the strength of magnetic fields. I'll let the
professional(s) discuss that.
<cough>Johann Beda</cough>

If somebody wants to make certain the data on a hard drive is not
readable, the best way to do this is to remove the magnetic particles
or render the platters inaccessible. Sandpapering the platter surface
down to bare metal is particularly appealing to me. One method we use
at my work is a drill press. Others have suggested methods that
require more physical force (e.g. sledgehammers). 100 fathoms of
seawater would work too. YMMV.

(This is a fun thread!)

At 5:23 PM -0700 7/13/06, Edward Reid wrote:
>>We tried to use it to erase SyQuest cartridges and floppies, and
>>amazingly, never managed to hurt either.
>
>The heads on a disk drive fly about a micron off the surface.
>Magnetic field intensity varies with the inverse square of the
>distance. So a magnet an inch from the surface is attenuated by
>twelve orders of magnitude compared with the write head (which of
>course is not as strong a magnet). Even if you can get it to with
>1/100 inch of the surface and your magnet is 100 times as strong,
>you're still short by six orders of magnitude.

Quite right. (And I'd hoped that somebody would provide the proof
with the math.)

>There are (or at least used to be) such things as bulk tape erasers.
>So with a strong enough magnetic field, such things can be done. I
>don't know the numbers. Of course, this assumes that bulk erasing
>really worked ... I don't recall anyone ever checking the results!
>Perhaps it was all psychosomatic. ;-)

When I worked in network television we had a bulk eraser on the other
side of a drywall with steel frame interior wall from one of our PPC
6100 PowerMacs. I guarantee that bulk erasing will wipe the data on a
videocassette passed through the machine, and it will bend the
electron beam in the CRT, but it will not affect the hard drive.

dano said:

>We tend to overestimate the strength of magnetic fields.


This is a great thread...because it has to do with destroying things!
8-{D

Just as another interesting data point, a bunch of years ago I worked in
a car stereo store as a salesman. One day I absent-mindedly set down a
demo casette tape on the hind end of a 15-inch sub-woofer speaker. For
those who don't know, automotive sub-woofer's have huge permanent magnets
on their hind-ends. (In fact, in those days, the bigger the magnet, the
more impressive the speaker was to customers. Even though the size of
the magnet has little to do with the quality of the sound in reality.)

The casette tape would still play, but the recorded material was
unlistenable. The music playback wavered badly in speed and volume.

Seeing an opportunity to have more fun, I put a used 3.5-inch floppy disk
on the magnet of the same speaker. The data on the floppy was entirely
undamaged.

From that experience, I wouldn't be at all surprised to find that a hard
drive might come out unscathed from an encounter with even a very large
magnet.



Randy B. Singer
Co-Author of: The Macintosh Bible (4th, 5th and 6th editions)

ROUTINE OS X MAINTENANCE
http://www.macattorney.com/ts.html

Should change the thread name to "Destroying a dead hard drive"

Has anyone suggested 60 minutes in a 375 F oven?

How about the home Bar-B-Q outside at least the smell wouldn't drive
everyone out of the house?? X;{ One could make it red hot on the
burner of a Propane Grill in short order.

There are 3 choices :
1. The bridge is damaged
2. the drive's "driver" has corrupted
3. the drive is damaged

Others have written about 1 and 3 .

Sometimes the driver becomes corrupt and the answer is to somehow
MOUNT the drive on a desktop.

In my experience , sometimes when one utility will not recognise the
drive, another utility will and then mount the drive.

I have used at various times in Mac OS 9

Apple DISK UTILITY

  SPEED TOOLS <http://www.speedtools.com/index.shtml>

  HARD DISK TOOLKIT maker has closed up, but I have a copy .

DISK WARRIOR



So if you want / need to recover the drive try those utilities by
firing up a Mac with Mac OS 9.

If you need to try Hard Disk Toolkit i can probably help .

Bob Howells
Perth
Western Australia

The neodymium magnets in even a 40M hard drive mechanism are quite useful.

If you're going to the trouble to disassemble a drive mechanism to get at the platters (to sand them, for example) you might as well go all the way and rip out the pair (usually) of magnets at the end of the voice coil, at the far end of the read/write heads. You could use them to wipe data from the platters.

The strength of these magnets, however, makes them very useful around the house, particularly in a workshop: mount them securely to the ceiling to hold various items in a relatively accessible way. I have hammers hanging from such magnets - and it takes far more force to pull them straight (down) off of the magnets than gravity will ever exert on the items...

Be careful handling a pair of these magnets - you can pinch the flesh of your hand painfully when the magnets realise they're within range of another of the same species - and are feeling amorous.

On Jul 18, 2006, at 1:49 PM, Charles Harrison wrote:

> Should change the thread name to "Destroying a dead hard drive"
>
> Has anyone suggested 60 minutes in a 375 F oven?
>
> How about the home Bar-B-Q outside at least the smell wouldn't drive
> everyone out of the house?? X;{ One could make it red hot on the
> burner of a Propane Grill in short order.

Why not just a couple of minutes with a ball peen hammer???

Charles Harrison wrote:
> Should change the thread name to "Destroying a dead hard drive"
>
> Has anyone suggested 60 minutes in a 375 F oven?
>
> How about the home Bar-B-Q outside at least the smell wouldn't drive
> everyone out of the house?? X;{ One could make it red hot on the burner
> of a Propane Grill in short order.
>
Sorry but I'd never put electronics in a oven or grill or whatever where
food might ever be cooked. Way too much chance of interesting chemicals
being vaporized or out gassed. I'd not even want to be around such
things when they are heated.

This from someone who is old enough to remember how much fun you could
have with mercury, thermite, and other interesting thing. Of course that
could just be me being afraid I'm near the limit on way too many
chemical exposures. :)

> From that experience, I wouldn't be at all surprised to find that a hard
> drive might come out unscathed from an encounter with even a very large
> magnet.

Well, some time (very long time) ago, it was recommended when your CRT
monitor showed distortions due to magnetic fields in its surroundings to
shield the CRT with a sheet of metal. Usually the distortions vanished.

As a hard drive is enclosed by a metallic housing, I suspect the platter is
shielded by the housing as effective as the CRT by a sheet of metal.

Udo

> Sometimes the driver becomes corrupt and the answer is to somehow
> MOUNT the drive on a desktop.

Yes, a corrupt driver is what happened to my hard drive back in
1994... But while my two "current" computers have Classic installed,
neither will boot into OS9.

I don't remember reading about "drivers" since OSX -- they seem to
have disappeared under the hood somehow.

As for bulk erasers -- I remember using them back in the days, but I
used to think that more than for erasing, they were meant to put the
oxide particles back in their place so that nothing from the previous
recording would muck up the new one... At any rate, it's great to
know that magnets aren't such a big deal in the digital realm... I no
longer have to get antsy about the phone sitting next to the
computer, or what have you :-)

On the downside, it probably means that there isn't a gray area
between either mounting the drive first to erase it or physically
destroying it. Which brings me to the bridge diagnosis which I'd
probably try for first. The main reason I didn't yet (besides
personal time-management issues ;-) is that it would void the
warrantee (opening the enclosure), but I'm thinking that it would
probably cost less than buying speed tools or tech tools pro, given
that neither Apple's Disk Utility nor Disk Warrior could see the
drive as it is (at least in OSX).

Thanks for the offer, though, and for all the wonderful information...
-S

Udo Huth wrote:
>> From that experience, I wouldn't be at all surprised to find that a hard
>> drive might come out unscathed from an encounter with even a very large
>> magnet.
>
> Well, some time (very long time) ago, it was recommended when your CRT
> monitor showed distortions due to magnetic fields in its surroundings to
> shield the CRT with a sheet of metal. Usually the distortions vanished.
>
> As a hard drive is enclosed by a metallic housing, I suspect the platter is
> shielded by the housing as effective as the CRT by a sheet of metal.

Sorry but no. That metal shield didn't do much unless it was a ferrous
metal with a high ??? (I forget the term). And the last thing you want
is a disk drive encased in such stuff which would tend to distort the
design of the heads and the arm magnets. All the drives I've taken apart
in the last 10 years or so seemed to be cast aluminum with a thin, very
bendable cover.

We had this crt situation a few years ago in a converted ware house
where the high voltage for the area ran just outside the windows. It is
3 phase with the wires closely spaced in a triangle. In the summer when
the loads got unbalanced due to construction and A/C loads the resultant
fields would shake our 20" CAD crts. These window (sitting next to)
users got the first LCDs in the office and life was much better after
that. We tried some heave sheet steel for a while but it's affect was
minimal most of the time.

On Jul 19, 2006, at 2:54 PM, David Ross wrote:

> thermite

Thermite is really good for welding Boston MTA trolleys to the
tracks. (That's the main reason the line past MIT's building 7 was
trackless trolley by the time I got there. In at least one episode,
MTA cut out the section of track containing the welded trolley,
loaded the track plus ties plus trolley onto a truck, and hauled it
away. It took about 20 students: 2 or so welding and the others
entering at the front and exiting at the rear (repeat until done).)

The venture in which the switches at Scolley Square were welded to
divert westbound traffic back to the east was even more destructive.

I concur with the idea of not heating electronics in food prep areas.

   --John