12 ms·
Can I erase sensitive data on an old hard drive with Neodymium Magnets?
- tinus_hn 9y agoEven 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 and platters.
- Filligree 9y agoI 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.
- Johnny555 9y agoHard drives automatically remap bad sectors, so even if you overwrite 100% of the accessible data, you may still have left pieces of data in remapped sectors that weren't overwritten. If your drive supports the SECURITY ERASE feature, then it should overwrite those blocks too. Though if you really want to sell or give your drive to someone else, the best thing to do is to use full disk encryption from the beginning, then there will be no plain text data on the drive.
- cmurf 9y agoAnd 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.
- magnat 9y agoHard 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 https://www.youtube.com/watch?v=-bpX8YvNg6Y
- FRex 9y agoI instantly though it was this (hilarious) one instead: https://www.youtube.com/watch?v=1M73USsXHdc https://www.youtube.com/watch?v=1M73USsXHdc
- jacquesm 9y agoThey should have used a plasma torch. Legal, relatively easy to contain too (just put a water bed below it).
- allenz 9y agoEntertaining talk, but the best method is to discard the key for your fully encrypted disk. It's 2017, all your disks use FDE, right?
- zaarn 9y agoSSDs internally yes. Any modern SSD simply uses some random key unless you specify another one. Shredding is as simple as telling it to shredder the key, end of story. Some harddrives do this too, I believe but it's not as widespread yet.
- tscs37 9y agoIf 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 the pieces in a fire and then throw away the leftovers. Probably overkill but I want to be certain.
- readams 9y agoNormally 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.
- qubex 9y agoHe forgot to mention he has purchased a steel foundry for the triennial purpose of zeroed-out drive disposal.
- Spooky23 9y agoYou 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!
- ben-schaaf 9y agoThere's a great defcon talk exploring different methods to completely destroy a drive: https://www.youtube.com/watch?v=-bpX8YvNg6Y https://www.youtube.com/watch?v=-bpX8YvNg6Y.
- nilram 9y agoA friend uses a saws-all (or something of that ilk) and cuts them in half. I'm figuring on taking my old drives to him for that treatment. I don't want to resell them and have a casual snooper recover my data, and I'm not of enough interest for anyone to piece the halves together.
- bluedino 9y agoI use a drill or press at work to do the same thing. Bens s drive in half or put a couple holes in the platters
- Johnny555 9y agoSomeone once suggested to me drilling a hole through the platters, then using that hole to fill the drive with salt water. I don't know if the salt water really adds to security, but for the type of data on my drives, just drilling the hole seems like more than enough - no one is going to spend $1000 to recover my 2014 tax return from my drive since there are far easier ways to get my personal data.
- Symbiote 9y agoWhat's the risk from simply writing over the drives with zeros, and sticking them in the electronics recycling? I don't think anything I or my employer has would be worth the effort to recover.
- AnIdiotOnTheNet 9y agoRight? What are the people in this thread doing that they're worried someone would take the time to employ theoretical, if not entirely hypothetical, recovery methods against a zeroed disk?
- golem14 9y agoZeroing out a 4tb drive takes some time. Sometimes you might be in a hurry ;)
- FRex 9y agoHere are few experiments with a 6 inch neodymium magnet with few devices: https://www.youtube.com/watch?v=_yEu2R1gYSs https://www.youtube.com/watch?v=_yEu2R1gYSs https://www.youtube.com/watch?v=4l-6qWaZpVQ https://www.youtube.com/watch?v=4l-6qWaZpVQ
- nixpulvis 9y agoThis 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.
- keithpeter 9y agoAlas, such a strategy will not work at universities local to me (UK). They specifically exclude computer malfunction as grounds for extenuating circumstances.
- golem14 9y agoFor quickly destroying hard drives, drive big nails through the entire case in several places. Restoration is at least very manual and annoying, in many cases not worth the effort. If you need more security, building a simple furnace isn't too hard: http://eecue.com/c/driveslag http://eecue.com/c/driveslag
- mirimir 9y agoYou don't need to go that fancy. Just use a small steel drum, with holes punched around the bottom, sitting on bricks. Burn dry hardwood, plus occasional chunks of paraffin. Everything burns off, except for the steel.
- EvanAnderson 9y agoHere'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 the PC immediately when the whine started. BIOS would no longer detect the disk on that machine, or any other I tried it on (on both USB-to-PATA and honest-to-goodness motherboard PATA controllers). The drive spun up but made a repeated ticking sound (I assume seeking back and forth looking for servo tracks). I sent the drive to Kroll Ontrack (because, stupidly, I had billing data that wasn't backed-up on the drive). The report I received back indicated that 80% of the drive's sectors were unreadable. As an aside: The data I was looking for was ASCII text and Kroll Ontrack was completely unhelpful in just sending me a bitstream image of the drive so I could grovel thru looking for data I needed. Being plain ASCII, their "file carving" tools didn't locate any of the data. (They sent me a "preview" of the data they'd located, and while it got lots of Microsoft Office-format files, it didn't have any ASCII text files). I offered them a 3x multiple of the rate they asked for file-level recovery to simply send me the bitstream image of the disk that they'd already made. They wouldn't do it, and wouldn't even let me pay to talk to somebody who understood what I was saying. I ended up taking a major loss on the billing data I destroyed. I'll never recommend them to anybody. I won't ever play with neodymium magnets around spinning rust media again.
- dpedu 9y agoFrom 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.
- quickben 9y agoBut it will mess up the power flow. Misbehaving powesupplies destroy HDDs.
- dboreham 9y agoNo. You need to cast it into the fires of Mordor. Or something similar.
- ravenstine 9y agoWhat I've done is not that dissimilar. It's pretty easy to build a furnace out of basic household items. With charcoal and a leafblower, you can get it up to a temperature where an entire HDD will melt or burn.
- gruturo 9y agoSomething similar is indeed the right answer here. You have to take the material above its curie temperature (https://en.m.wikipedia.org/wiki/Curie_temperature https://en.m.wikipedia.org/wiki/Curie_temperature) and then according to physics all preexisting magnetic information is lost.
- KaiserPro 9y agoThermite, both fun _and_ effective.
- cmurf 9y agoI think magnets could compromise the read/write head, or other electronic on the drive. So why not just mulch the drive with a grinding service? If you're looking to reuse the drive, use one of the NIST SP 800-88 Revision 1 recommendations. It lists the methods in the preferred order. Ideally the drive supports ATA crypto secure erase, where it just wipes the DEK and KEK, poof, in effect the crypto encoded form of you data can no longer be turned into plain text. You can mimic this with software FDE (Bitlocker, LUKS/dm-crypt, Filevault). Fast. But they also say it's adequate to use the other kinds of secure erase, because other than firmware bugs/exploits it's the only way to erase sectors not assigned an LBA, e.g. sectors that once had an LBA, had data written to them, but subsequently failed overwrite and the LBA remapped to a reserve sector, leaving data on a sector that cannot be overwritten via SATA commands.
- mark-r 9y agoIs it really necessary to overwrite the data multiple times to erase it? With the densities provided by today's hard drives, the techniques you used to be able to use to get partially erased data are routinely used by the disk drive itself for normal reads.
- FooHentai 9y agoWhat'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.
- KozmoNau7 9y agoWhy 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?
- FooHentai 9y agoTimeliness, 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!
- abrookewood 9y agoIt's totally not required to wipe it/over write it more than once. I wish I could find the reference, but someone made a fairly comprehensive attempt to read data that had been over written once and they couldn't detect anything.
- crx087 9y agoNot true, at least not under many conditions. The required equipment makes magnetic data unlikely to be recoverable except in exclusive cases where certain government agencies with sophisticated labs get involved, but in short, storage leaves lasting (trace) physical changes behind. SSDs and operating systems without proper Secure Erase support can very easily leave behind complete data.
- snvzz 9y agoJust encrypt each and every one of your drives. It makes their end of life that much easier.
- amluto 9y agoA 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.
- jimmyswimmy 9y agoTFA 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.
- coretx 9y agoMicrowave ovens do wonders.
- cptskippy 9y agoI normally unsubscribe from junk mail and advertising from e-commerce sites, KJ Magnetics is one of the few exceptions. I always look forward to their emails and blog entries.
- tfha 9y agoBest 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
- rgbrenner 9y agomost ssds already encrypt data with aes.. you can just send a command to the drive telling it to erase the key.
- darkmighty 9y ago> such that loss of a single bit means the original key is unrecoverable That can't be right (I don't know anything about this though). If you control the data (with a non-interactive non-destructive decryption process), a loss of a single bit just means you have to test two possible keys. In terms of brute forcing, the security is the same per number of bits lost. The benefit of using a large key would be that if you lose a certain fraction of your key (say 10%), then that would correspond to more bits (as long as you erase 128 or more bits you'd be fine). Also beware of key stretching, use it only when absolutely necessary. Key stretching doesn't modify the ratio of work necessary for your encryption/decryption vs the work necessary for brute forcing -- i.e. it doesn't improve the security factor. You're essentially doing an economic defense vs a mathematical one, and hoping that computers won't improve and your attacker isn't willing to spend much relative to what you spent.
- wheresmyusern 9y agoeven if you drill a hole in the drive, data can still be recovered from it. anything that leaves large pieces of drive intact really isnt ideal. over the years i had collected dozens of platters from both myself and other people. for some reason, when i was younger i was obsessed with collecting hard drive magnets and also smart enough to understand that i probably shouldnt throw the platters away. so a few years ago i decided it was time to destroy all of these annoying platters that i have to worry about misplacing. i naturally assumed that it was going to be easy to find some kind of service, shredding or wiping, for hard drives or hard drive platters. there were no good options. so i tried smashing the platters into small pieces, and this worked for some of the thinner laptop hdd platters. one strong hit would break them into millions of tiny pieces. but most of them just bent or dented. and to thoroughly bend and dent the whole surface of all the platters would be super annoying. so i decided i should just melt them -- they are made of aluminum which has a low melting point. it was surprisingly easy. just get an old coffee can or better yet a stainless steel gas cylinder or even a ceramic crucible. they arent too expensive as far as i know. i used a can. then just surround the can with some bricks for insulation and apply a normal blow torch. set the torch down so it blows into the void between your vessel and the brick jacket. after the platters are melted you can even cast them into something, like a belt buckle. its all a bit silly, but it does feel nice to know that it is literally impossible for anyone to ever know what was on those platters.
- JTechno 9y agoHDD's are shielded with mu-metal: https://en.wikipedia.org/wiki/Mu-metal https://en.wikipedia.org/wiki/Mu-metal
- oldandtired 9y agoThere are techniques used to recover previously erased information on HDDs. These techniques have been available since the 90's. The best way to make it unrecoverable is to melt the disks by the use of whatever techniques you have available, including ox-acetylene torches (the favoured method for the company at the time I was working for them), putting into a furnace (as suggest by others here), etc. The problem with erasure is that there is residual amounts of magnetic fields that can be picked up by the right equipment. In the day, it was reported that they had success with recovery of information that had been overwritten by 8 - 10 times. It just took a lot of patience to do so. Those who want to recover this information will have that patience.
- rasz 9y agoThese techniques are theoretical from the time HDDs needed a user low level format(think RLL controller in your XT), and even then a myth nobody ever demonstrated in practice.
- rodgerd 9y agoAn angle grinder through the drive, repeatedly, may or may not be the most effective mechanism, but the sparks sure are pretty.
- OliverJones 9y agoHIPAA - 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.
- rasz 9y agoso secure, guess nobody heard of $100 label printers
- X86BSD 9y agoI think I’d rather store the data on a gbde encrypted disk and simply toss it when I’m done. Then I know the data can’t be read.
- codewritinfool 9y agotake it apart, screw the platters to railroad ties. use belt sander on platter. flip the platters over. repeat. burn sandpaper. take a hammer to platters to seriously deform them and throw them in the trash. not recoverable, imo.
- Lramseyer 9y agoI worked in the HDD industry, doing signal processing for a few years. HDDs are pretty much magical. It's insane how delicate, yet robust it all is. But to put things into perspective with some numbers, the write heads on a modern HDD use somewhere on the order of 50 mA of current. That may sound like a reasonable amount until you consider that the magnetic field [flux] is condensed down to a 60 x 20 nm area. It usually takes a little over 1 Tesla to flip the magnet. I have been out of the Industry for a little bit now, but things are moving towards a magnetic substrate that has a smaller grain size (allowing smaller bits at a similar SNR) but a coercivity well over 3T at room temperature.
- zkms 9y ago> HDDs are pretty much magical. It's insane how delicate, yet robust it all is. Absolutely. It's bloody amazing how my laptop has a device with finger-sized actuators that read/write bit cells that are about as small as couple-year-old semiconductor feature sizes -- and that can survive mistreatment that one doesn't usually associate with micromanipulators.
- richev 9y agoWhen I had a few old hard drives to dispose of I drilled several holes in each one, through the case and platters, then filled them with water and left them outside for a few days so that anything that might rust would do so.