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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?

#121

Post by harshreality »

quickben wrote: post #113
harshreality wrote: post #108

Earlier quoted context omitted.

Nobody is suggesting that electromagnetic theory is false. The question is whether there's really a danger from HDD magnets in motion relative to nearby electronics or HDD platters. - HDDs often live right next to each other (separation of roughly 1cm, front to back). - Power supplies and their induction coils are right next to the drives in some cases, including for instance consumer grade NAS boxes. - HDDs tend to…

The magnetic head that writes to the disk, is fairly small and close to the platter. The flux is very contained. So that part seems negligible in the overall scheme of things.

Who's talking about the field from the magnetic read/write head(s)? This is about the permanent magnets built into spinning hard drives, and what those permanent magnets might do to nearby disk platters, or, when in motion, might do to coils of wire in nearby electronics.

Either some extremely unfortunate and rare positioning and orientation and motion of the magnet occurred, which barely exceeded the design limits of the drive or power supply or other circuitry (or maybe the laptop hdd or circuitry was shoddy and shouldn't have had a problem but did), or this is a major problem that's gone unappreciated among computer and NAS builders for decades, or it was an extremely unlikely coincidence.

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

#122

Post by linkmotif »

EvanAnderson wrote: post #111
linkmotif wrote: post #94

Earlier quoted context omitted.

Why wouldn’t they send you the image??

It was around Christmas, and a lot of people seemed to be out of the office for vacation. My sales rep was not technical and didn't understand what I meant when I asked for the "bitstream image" or "raw image" of the drive. I kept pressing, leaving voicemails in which I said stuff like "Look-- you don't know what I'm asking for. Send this to somebody in your engineering department and they'll know what I mean. I want…

That sounds really frustrating to say the last! Thanks for sharing. Interesting stuff.

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

#123

Post by Houshalter »

tscs37 wrote: post #98
Turing_Machine wrote: post #97

Earlier quoted context omitted.

A friend of mine who was a military secure comms guy back in the 80s told me that if their position was about to be overrun the procedure was: 1) Fire a twelve gauge shotgun slug into the drive (these would have been external drives). 2) Place a thermite grenade on drive, pull pin. 3) Bug out.

I wouldn't bet on that being a 100% deletion. It'll probably trash most of the data but not all. Thermite grenades aren't very good at melting a huge chunk of metal either, sure it'll go straight through a machine block but it won't melt the entire machine block. To destroy all data on a harddrive all parts of the platter must be destroyed and heated to their Curie point.

Terry Pratchett had all his unpublished works destroyed with an antique steam roller: http://mashable.com/2017/08/30/terry-pratchett-hard-drive-st...

Any chance that could be recovered?

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

#124

Post by FooHentai »

KozmoNau7 wrote: post #107
FooHentai wrote: post #30

Earlier quoted context omitted.

What's your threat model? Data must not be recoverable for at least the next X years, or data must not be recoverable within any future time frame, no exceptions? For the former, you're absolutely right. For the latter, multiple-pass overwrite provides greater assurance than single pass. Following that up with physical destruction of the platters provides further assurance.

Why even bother with overwriting the data if you're just going to physically destroy the platters and/or heat them beyond their curie point anyway?

Timeliness, usually. Destruction is usually a batch job so if you care about risk of data exposure in the time lag between being able to wipe the drive (usually an online, relatively low-hassle activity) and destroying the drive, wiping is worthwhile.

Again, thread modelling is crucial. There may be no point wiping!

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

#125

Post by quickben »

ars wrote: post #116
quickben wrote: post #114

Earlier quoted context omitted.

Open a powesupply before your next reply.

What am I supposed to reply to? Instead, why don't you take a multimeter and see if you can measure any voltage (never mind current) by moving a magnet, by hand, near a single non-coiled wire.

Well honestly, I wrote that because I wasn't sure what to reply. I'm taking in five comments about power supplies, tons of wrapped wire, and I get a reply about a single wire.

Anyways, I apologise for being snappy.

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

#127

Post by tscs37 »

Houshalter wrote: post #123
tscs37 wrote: post #98

Earlier quoted context omitted.

I wouldn't bet on that being a 100% deletion. It'll probably trash most of the data but not all. Thermite grenades aren't very good at melting a huge chunk of metal either, sure it'll go straight through a machine block but it won't melt the entire machine block. To destroy all data on a harddrive all parts of the platter must be destroyed and heated to their Curie point.

Terry Pratchett had all his unpublished works destroyed with an antique steam roller: http://mashable.com/2017/08/30/terry-pratchett-hard-drive-st... Any chance that could be recovered?

I would say the chance of recovering any data is bigger than 0, yes.

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

#128

Post by SAI_Peregrinus »

EvanAnderson wrote: post #112
Waterluvian wrote: post #68

Earlier quoted context omitted.

I stack hard drives and they keep working.

Absolutely. Hard disk drives don't stick to your refrigerator (like a naked magnet does) either. My layman's guess would be that the fields generated by the magnets in opposition in the voice coil are somehow "balanced", so that the net magnetic field produced by the drive is negligible.

It's simpler than that. They're held in an iron ring. This confines the field nicely, the permeability of the iron is quite high.

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

#129

Post by keithpeter »

derefr wrote: post #86
akvadrako wrote: post #39

Earlier quoted context omitted.

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.

Usually with full-disk encryption, your supplied encryption passphrase is used to encrypt a single sector (or redundant set of sectors, spread across the disk) containing a much larger master key, which is in turn used to encrypt the rest of the sectors. When you change the disk password at the OS level, the master key remains the same (which is why you don't have to wait for the disk itself to re-encrypt); the singl…

Yes, I'm assuming that if I 'write zeros' over the SSD when parting with the device that I have destroyed the keys.

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

#130

Post by rasz »

OliverJones wrote: post #72

HIPAA - regulated health data requires physical destruction of retired hard drives. Usually this is done in sight of a video camera. The operator shows the drive's serial number to the camera and then drops it into the grinder. CMS (Centers for Medicare and Medicaid Services) can require proof of destruction. That video does it.

so secure, guess nobody heard of $100 label printers
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