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Can I erase sensitive data on an old hard drive with Neodymium Magnets?

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Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#31

Post by jimmyswimmy »

amluto wrote: post #27

A ferromagnetic cage such as a hard drive enclosure can shield against magnetic fields pretty well. The field lines are concentrated in the enclosure and mostly avoid the inside. I would imagine you need to open the drive up to have much effect.

TFA said specifically that they could tell that the larger magnets were imposing a field inside the drive itself, and they could tell it was so because they could hear sounds coming from inside the drive. They presumed that the sounds were generated by deflection of the discs under the magnetic field. Therefore it is evident that the field is penetrating through the outer case.

They surmise that it was the higher coercive ty of modern drive plates that causes them to be resistive to reprogramming bits with a static magnetic field.

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#32

Post by dpedu »

EvanAnderson wrote: post #17

Here's my anecdote: In 2006, while sitting at my desk playing a video on the hard disk drive of my Thinkpad T22, I held a single neodymium magnet (harvested from an old hard disk drive) about 6 inches from the left side of the unit (where the ~40GB-ish Travelstar 2.5" PATA disk was located). The video froze, Windows XP blue-screened, and the hard disk drive started emitting a ~10Khz whine. I jerked my hand away from…

From 6 inches away? Unless this was a hockey-puck sized magnet I'm calling it a coincidence.

> (harvested from an old hard disk drive)

Okay, this is making even less sense. "Hard drive magnets", in a drive, are millimeters from the spinning platters. I refuse to believe that the same magnet, moved 6 inches away from the computer caused catastrophic damage.

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#33

Post by cmurf »

Filligree wrote: post #7
tinus_hn wrote: post #2

Even if the test would have succeeded, this is a bad idea. With a magnetic swipe card that you demagnetize so it is no longer read successfully, you may well be able to recover the information using a better reader. Depending on drive age the same may be possible using a hard drive. The best option for modern drives is still to use software to wipe the drive and if reuse is not required destroy the reading mechanism…

I won't say it's completely impossible, but modern HDD read heads are already close to our technical limit, and the signal they get is so noisy as to require extensive processing. There definitely was a period where labs could recover data this way, but I think it's passed.

And that's probably why the single pass of zeros is considered adequate, and why a single pass ATA Secure Erase or Secure Erase Enhanced is better than that.

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#34

Post by quickben »

dpedu wrote: post #32
EvanAnderson wrote: post #17

Here's my anecdote: In 2006, while sitting at my desk playing a video on the hard disk drive of my Thinkpad T22, I held a single neodymium magnet (harvested from an old hard disk drive) about 6 inches from the left side of the unit (where the ~40GB-ish Travelstar 2.5" PATA disk was located). The video froze, Windows XP blue-screened, and the hard disk drive started emitting a ~10Khz whine. I jerked my hand away from…

From 6 inches away? Unless this was a hockey-puck sized magnet I'm calling it a coincidence. > (harvested from an old hard disk drive) Okay, this is making even less sense. "Hard drive magnets", in a drive, are millimeters from the spinning platters. I refuse to believe that the same magnet, moved 6 inches away from the computer caused catastrophic damage.

But it will mess up the power flow. Misbehaving powesupplies destroy HDDs.

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#36

Post by EvanAnderson »

dpedu wrote: post #32
EvanAnderson wrote: post #17

Here's my anecdote: In 2006, while sitting at my desk playing a video on the hard disk drive of my Thinkpad T22, I held a single neodymium magnet (harvested from an old hard disk drive) about 6 inches from the left side of the unit (where the ~40GB-ish Travelstar 2.5" PATA disk was located). The video froze, Windows XP blue-screened, and the hard disk drive started emitting a ~10Khz whine. I jerked my hand away from…

From 6 inches away? Unless this was a hockey-puck sized magnet I'm calling it a coincidence. > (harvested from an old hard disk drive) Okay, this is making even less sense. "Hard drive magnets", in a drive, are millimeters from the spinning platters. I refuse to believe that the same magnet, moved 6 inches away from the computer caused catastrophic damage.

I will definitely concede that the 6" number may be an incorrect memory. It certainly may have been closer, but it wasn't right on top of the unit.

If it was a coincidence it was certainly well-timed. I don't have the Thinkpad anymore, but I do still have some 2.5" PATA drives. It might be interesting to test this and make a video.

Here's a picture of the magnet in question (it holds stuff to my refrigerator now), w/ a penny for scale: http://mx02.wellbury.com/misc/20171203-Magnet_of_doom.jpg

This magnet was pulled from a Micropolis 9GB SCA-II 3.5" low-profile drive dating from roughly 1998 (I had a crap-ton of these drives and, as they died, I pulled their magnets, so I have a bunch of these). These particular magnets will stick to each other thru my 3" thick butcher block table. They are physically larger (substantially thicker) than the ones I've pulled from newer drives.

Edit:

I assume that the data and servo tracks written to the drive are done so in the presence of the magnetic flux of the magnets supporting the voice coil. I always just assumed that adding a substantial new source of magnetic flux (the magnet in my hand) either induced a current or magnetized some component in the drive.

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#37

Post by cptskippy »

quickben wrote: post #34
dpedu wrote: post #32

Earlier quoted context omitted.

From 6 inches away? Unless this was a hockey-puck sized magnet I'm calling it a coincidence. > (harvested from an old hard disk drive) Okay, this is making even less sense. "Hard drive magnets", in a drive, are millimeters from the spinning platters. I refuse to believe that the same magnet, moved 6 inches away from the computer caused catastrophic damage.

But it will mess up the power flow. Misbehaving powesupplies destroy HDDs.

So a magnet held 6 inches away from the PC did more damage than the one inside the HDD literally inside the PC?

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#38

Post by nixpulvis »

keithpeter wrote: post #28
nixpulvis wrote: post #15

This is exactly how I got out of a final project in middle school. Wiped my HDD with a Neodymium magnet right before the deadline and claimed my computer was "broken"... Of course this wasn't done for highly paranoid reasons where I needed to ensure the data was really all gone, but funny story nonetheless. People are more sympathetic when they think a computer "randomly" stopped working.

Alas, such a strategy will not work at universities local to me (UK). They specifically exclude computer malfunction as grounds for extenuating circumstances.

This was back in like 2005 or something too...

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#39

Post by akvadrako »

keithpeter wrote: post #26
tscs37 wrote: post #4

If you want to get rid of a harddrive with sensitive data I would first suggest that one gets familiar with the thought of not being able to sell it as used. Personally for my drives, I use Boot and Nuke to erase the drive three times, first with zeroes, then with random data, then with zeroes again. After that I disassemble the drive, put a strong magnet over each platter, shredder the drive into almost powder, burn…

How about whole disk encryption? When it is time to move on, one simply forgets the passphrase and reformats the drive. Seriously: that is what I'm doing with ssd drives. Anyone know of any issues?

Well your password could be brute-forced unless it's really long and random (about 20 chars). There might also be flaws in the encryption code. And changing it later won't work, because old sectors might still be recoverable, even if they are overwritten.

Re: Can I erase sensitive data on an old hard drive with Neodymium Magnets?

#40

Post by moonbug22 »

keithpeter wrote: post #28
nixpulvis wrote: post #15

This is exactly how I got out of a final project in middle school. Wiped my HDD with a Neodymium magnet right before the deadline and claimed my computer was "broken"... Of course this wasn't done for highly paranoid reasons where I needed to ensure the data was really all gone, but funny story nonetheless. People are more sympathetic when they think a computer "randomly" stopped working.

Alas, such a strategy will not work at universities local to me (UK). They specifically exclude computer malfunction as grounds for extenuating circumstances.

Quite right, too.
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