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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?

#41

Post by 2muchcoffeeman »

cptskippy wrote: post #37
quickben wrote: post #34

Earlier quoted context omitted.

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?

Yeah, I hope people realise that everybody has these magnets IN their computer. You might have a NAS in which case you have several of these magnets much closer than 6 inches to the other drives and power supply and nothing happens.

Magnets near your or even on the computer do nothing.

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

#42

Post by kees99 »

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…

Most likely mechanism for this incident was:

1) external magnet messed up heads movement closed control loop (internal drive's magnets + voice coil + positioning marks on the platters), and as a result head actual position became different from what controller thought it was.

2) control loop tried to correct itself, repeatedly failing, all while head kept moving across the platters, while controller was still thinking it's elsewhere.

3) controller was writing to disk, so it overwrote data in highly irregular tracks that followed erratic head dance. some of that overwrote positioning markers.

4) when recovering, even though 99.9% of data was still there, controller failed to position the head on erased markers, so reported "unreadable sectors"

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

#43

Post by keithpeter »

akvadrako wrote: post #39
keithpeter wrote: post #26

Earlier quoted context omitted.

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.

I take the point, and my passphrase is a phrase so perhaps subject to dictionary attack of a sophisticated nature. At the end of the day, this is all about the level of risk one expects. Mine is 'don't want some random petty thief finding my credit card number' rather than 'don't want some government agency reading my old emails'.

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

#44

Post by didhshz »

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…

You didn’t hold a magnet 6 inches away from your HD.

You held a magnet 6 inches away from a plate spinning at 5400 rpm.

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

#45

Post by Scramblejams »

2muchcoffeeman wrote: post #41
cptskippy wrote: post #37

Earlier quoted context omitted.

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

Yeah, I hope people realise that everybody has these magnets IN their computer. You might have a NAS in which case you have several of these magnets much closer than 6 inches to the other drives and power supply and nothing happens. Magnets near your or even on the computer do nothing.

Magnets induce a current when moved relative to a conductor. The magnets you mention aren’t moving.

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

#46

Post by tfha »

Best method is to use LUKs and then wipe the master key. Luks has a forensic stretching technique to take a 32 byte master key and stretch it to 1 MiB, such that loss of a single bit means the original key is unrecoverable.

That really helps you wipe things like SSDs which can copy and migrate data, and make it hard to be certain you destroyed a sector

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

#47

Post by Spooky23 »

readams wrote: post #5
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…

Normally you'd want to throw the remains into a volcano but I guess if you feel safe just throwing it away then you do you.

You jest, but jackass security people would probably be dissatisfied that your PII might be accessible to some alien race when after the earth explodes in 5 billion years and some remanent of data is somehow recoverable from an asteroid made of cooled lava.

I recall one datacenter consolidation project where the hard drives from decommissioned servers were zapped with a degaussing device, shredded, and then somebody signed off that they were dumped in a furnace somewhere. (At some ridiculous expense)

Meanwhile, the normal operation bins of drives that were in little blue bins for collection where just picked up and moved by the moving men, and are probably still in some closet in the new facility!

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

#48

Post by visarga »

readams wrote: post #5
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…

Normally you'd want to throw the remains into a volcano but I guess if you feel safe just throwing it away then you do you.

In India we use elephants for 100% certainty.

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

#49

Post by jacquesm »

FRex wrote: post #12
magnat wrote: post #3

Hard disks are surprisingly hard to destroy on-demand. There was a DEF CON 23 talk [1] exploring ways to quickly wipe your servers in situ using physical methods. [1] https://www.youtube.com/watch?v=-bpX8YvNg6Y

I instantly though it was this (hilarious) one instead: https://www.youtube.com/watch?v=1M73USsXHdc

They should have used a plasma torch. Legal, relatively easy to contain too (just put a water bed below it).
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