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I have a broken HDD that contains sensitive data. Since no software can access the disk, I can't wipe it using any of the tools generally suggested.

Breaking the disk physically into very small pieces would probably suffice, but that would require some good tools to do. Just waving a magnet around the disk might still leave the data recoverable by data recovery experts, or am I wrong?

What's an effective way to clear the sensitive data?

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Lifehacker has an article on this subject –  mjrider Apr 29 '11 at 20:31
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up vote 15 down vote accepted

You're correct; physical destruction is the only good way to do this (you'd need a magnet so strong that it's not feasible to get one for most people unless you're on staff at the Large Hadron Collider). Professional disposal operations generally do this with an industrial metal shredder. For you, bending the platters with a hammer, sandpapering them, and then running a drill through them in multiple points is sufficient to stop anything but advanced forensic data recovery. If you're really concerned about even that, or you just want style points, you might try thermite. It is usually sufficient to melt the platters entirely.

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Let no man say that SU does not provide help to even the most (seemingly) felonious-helpingly of questions. :P –  Ragnar Apr 28 '11 at 14:22
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@Ragnar - I just read it uncharitably. Sorry to be a buzzkill! –  Shinrai Apr 28 '11 at 14:27
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I had a hard time choosing which of the many excellent answers to accept. In the end I accepted this because the combined hammer-sandpaper-drill is very easy to do and might be more secure than doing just one of them... –  dancek Apr 29 '11 at 22:42
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Save time, I just use a 5lb hammer.

Note: wear safety goggles.

enter image description here

Or buy one of these

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You might want to add safety goggles to this equation. :) –  Shinrai Apr 28 '11 at 18:25
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The technical name is BFH. –  Paperjam Apr 28 '11 at 19:33
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I actually had a bunch of old disks that I had to destroy recently. I took the platters out, which are primarily aluminum, and put them in a buck of muriatic acid. Literally ate them away. –  KCotreau Jul 9 '11 at 0:19
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On newer drives, even the high-power magnets I used to use don't work anymore to erase the disk.

If you have a spike, or similar object (hard metal that is pointed, think of a nail that is much bigger) and drive it through the center of the chassis with a hammer. That will bend the platers and damage the heads making it extremely difficult to recover.

A land stake from the hardware store should work for this.

Dispose of the board separate from the drive. This way any encoding information about the drive recorded on the controller will not be available making recovery exponentially more difficult.

After all that, you can safely send the remains to a computer recycler for shredding.

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Welcome to SuperUser! This is a good answer, I hope you continue to contribute. Also, FYI, it isn't necessary to sign your posts - we can all see your username. –  Shinrai Apr 28 '11 at 14:27
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Apparently the method a certain british university uses is drilling a hole through it. Failing which, thermite.

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+1 for thermite –  ephilip Apr 28 '11 at 17:00
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+1 for drilling a hole through it, while a very good forensic company could read the unholy parts they're gonna charge a fortune to read something with ragged holes in thats likely to damage their very expensive kit. Make sure you're drilling a couple of holes in the platter though! –  Robb Apr 28 '11 at 19:30
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We use a small drill, and drill in several spots at the University I work at where sensitive data is a big thing. –  KronoS Apr 29 '11 at 3:50
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In addition to all the advice above mentioning physical demolition, I would like to add putting the platters in an oven at the highest possible temperature for ca 20 minutes. IIRC, at those temperatures (if sustained) the magnetic information is lost.

If you think that is insufficient, heat up the platters over an open flame until they more or less glow (gas stoves are great for this!). At that point any information on them is essentially wiped. The flame of a candle could be sufficient, but would require some patience as you "anneal" the surface one square centimeter at a time.

Melting them with termite certainly will destroy the information, but is messy and dangerous and essentially not something you can do at home (in contrast to use a kitchen oven or gas stove).

Edit: Disclaimer: even if using an oven or gas stove is relatively safe from a fire hazard perspective, heating these platters might emit unpleasant and potentially toxic fumes. Make sure you have some good ventilation. Also, what I had mind when writing the above is to just heat the platters themselves, not the entire harddrive with controller card and all. (Disclaimer added as per Shinrai's recommendation).

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+1. I was just going to leave it at that but "+1" is too short to leave as a comment. –  Shinrai Apr 28 '11 at 21:41
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I opened a lot of drives, and they contain strong neodym magnets inside, so I suspect that trying to erase the data from outside is a waste of time. However, I would like to hear an expert, if just the electronics get destroyed by strong magnetism, or how much energy you need, to erase a hdd from outside.

But most drives have small stickers at the side, which cover small wholes, about as thick as a pencil. You can open the drive, fill it with sand, and turn it around sometimes. Or scratch the surface with a screwdriver or something like that.

hdds with hole on the side - more or less taken apart

I can recommend to open the drive, to get to the magnetic end of the head. Meanwhile, you get to the platters and can scratch them enough, to make it expensive as hell to recover some data.

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You could use a Propane Torch to do the job. You can melt the platters with it. Clean job :-)

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You should take it to a shooting range! What better way to improve your aim, destroy the disk, and have fun while doing all that.

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Shouldn't you wear safety glasses at the shooting range ANYWAY? –  Shinrai Apr 28 '11 at 19:39
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this is very dangerous, as it is possible for the bullet to ricochet off the hard drive, -1. I wouldn't do this even if you paid me. –  studiohack Apr 28 '11 at 20:49
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Kevlar is the answer –  Matthew Lock Apr 29 '11 at 1:41
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@studiohack i would :) –  Nate Koppenhaver May 2 '11 at 17:52
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Here is a step by step guide on how to take apart the drive and then sand the and destroy the platters to surely make the data unreadable.

http://web.archive.org/web/20130705190750/http://zatz.com/dominopower/article/how-to-destroy-a-hard-drive-on-purpose/

Also, instead of using the Torx screws, you can use a flat-head to remove the top of the hard drive.

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The only way to permanently destory data with no chance of any recovery regardless of how much effort you could put into recovery is to heat the platters to the Curie point. Granted, that's possibly beyond the point at which the platters will turn to molten metal, but for absolute certainty of destruction in a cost-is-no-object scenario I'd feed the disks through a hammer shredder and then melt the results into bars.

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It should be pointed out that it doesn't take much distortion of the magnetic signal to make the disks useless. The forensic techniques that used to be effective on a drive are now part of the standard electronics, just to get the densities required. A little sandpaper is probably perfectly effective.

If you want total security, just keep the platters and use them as coasters.

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Years ago, you used to be able to smack the center with a ball peen hammer, and this was enough to knock the platters off of the axis, and the minute someone came along and tried to power up the drive, the platters would get shredded internally when it tried to spin. Not sure if this is still a valid tactic or not.

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The site http://www.diskstroyer.com/ sells a kit that includes the equipment and directions about how to destroy the drive.

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According to wikipedia, sufficient quantities of concentrated hydrofluoric acid will completely dissolve glass, ceramic, and aluminum, the three most common substrates for hard disk platters.

It's not exactly a household item, though.

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Call a couple of your local document shredding companies. Most have gotten into the media destruction angle at this stage. Around here (New England) the average cost is about $10/disk for them to drop it into a monster chipper. Itsy bitsy pieces out the other end. If I do this for a client, I usually get a zip-lock baggie of pieces to bring back to them as proof, along with the receipt. I used to use several of the methods above, but for $10, it's not worth the time and effort.

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