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Are magnets good to use for destroying data?

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I learned that we shouldn't place magnets near the hard disk because the data will be corrupted or deleted. If this is true then can we magnets to destroy data instead of destroying the whole disk? Can we still use the hard disk after it has been placed near a magnet for a long time?

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This is a fascinating question and I'm going to be watching this for a response because I don't know for myself. I'm doubtful, though, or I'd think that would be listed all over the internet, and I've always understood that it's pretty darn hard to really delete anything.

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I do not know for a fact, but I would think that a magnet powerful enough to overcome the field inside of the drive will cause damage

All mechanical harddrives have a movable head which hovers between a set of high power neodynium magnets. If you apply a large enough magnetic force you can pull the head from one side to the other when the drive is off.

I do not know if it causes any physical damage when the drive is in operation, that would require some testing which I am not willing to do.

K-TRON

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Yes a powerful magnetic field will corrupt the data, however not complete loss (i.e. with PRML type drives you will have bits/sectors that are still aligned, it comes down to who are you trying to avoid reading it.) A side issue is that with strong fields you can screw up the drive head as well so it's not a good method unless total destruction is what your aim is. Generally for this I see people use industrial shredders (yes you put the whole drive in the shredder which mechanically destroys the drive) others I've seen use sanders to grind off the oxide layers on the platters themselves. Others may use a combination of the two plus incinerators however that's kind of old due to EPA issues.

If you are just looking at wiping a drive so that 99% of the people without corporate or government sponsorship can't get it, then using something like MHDD and doing a secure erase will do it (this function has been built into drives since ?2002? mainly at the behest of large corporate and government agencies). Good for most items probably not compartmentalized top secret stuff but then that's what the first items are for.

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Interesting topic. I had heard never to put anything magnetic on my computer desk or worse, on my tower itself. I did not realize that strong enough magnets could actually damage the drive, though. As someone else said, it is certainly not something I would experiment with.

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As I understand, speakers have magnets in them. Will the magents of the subwoofer, in anyway, affect the hard disk or any parts inside the tower if the speaker is beside it? What electronics should not be placed beside the tower that might affect the hard disks?

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yes they do (same with old fashioned CRT's to direct the gun) but they are generally way too low powered to really affect the media. To erase drives you're talking in excess of ~7000 Gauss right next to the drive surface but magnetic field falloff is rather fast with distance (look at maxwell's equations). Now that's not to say that you pick up a high-end 12,000 gauss magnet for a large speaker and then put the drive inside the speaker cabinet you won't have problems. ;)

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I think you will need to pick up a specialized magnets. I've tortured disks in the past by putting my server right flush next to the back of my rockford fosgate DVC 12" Stage 3 woofer, pound it for two hours, etc. but nothing ever happened to the disks and they worked fine.

Not to say they didn't suffer at all, if I had to guess, it's not the best thing to do to guarantee a long lifetime of the disk. But still, that magnet is HUGE (5KG or so?) with about 50Amps of power running right into the amplifier (500Watt RMS/1000 Peak). And being about 10 cm's from it (disk to back of woofer) caused no damage that could be detected.

So you might have a hard time with that. Personally, when I do work for clients on rented servers for clients (I'm in the backup world and also provide restore tests for clients), I use "DBAN" to erase the drives securely. I have it on a memory stick, boot the server from it, type "autonuke" and leave it for a day or so. ;) Works nicely on DL380G4/G5/G6 , etc. just a tip, if you might be inclined to go a bit different direction to ensure data destruction.

Off course, last resort, buying a big sledge hammer will also fix your problems within seconds!

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You'd need a big*ss magnet.

You can run an ordinary refrigerator magnet over a floppy disk or a credit card without damage. Now if you leave it there for an extended period you will destroy the data or render mag stripe unusable (same thing).

Now if you mean a harddisk sealed inside a standard casing, you would need a many, many times more powerful magnet and probably a fairly long exposure.

A sufficiently powerful magnetic field-- we use a purpose-built magnetic media degausser for this-- will wipe the whole disk and probably render the heads useless as well.

Normally, though, we just hit a disk with DBAN to destroy all of the data on it. This, of course, leaves the disk reusable, just with the previous data unrecoverable by pretty much anyone (send a disk with overwritten files, even with a single pass, to OnTrack/FADV/Driversavers/Gillware, and they will not be able to recover the data)... :)

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Off course, last resort, buying a big sledge hammer will also fix your problems within seconds!

This is what I love to do but I want to reuse my things as much as possible. I have old computer parts that are stored in the basement waiting to be sold out for scrap metal or reused by electronics or computer students.

Speaking of scrap metal, I will try going to the junk yard and request the owner if I can put my hard disk under the big magnet that loads the metals onto the train cars. I will test if that kind of electromagnet can erase or destroy the data inside the hard disk. Sounds like mythbusters for me.

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This is what I love to do but I want to reuse my things as much as possible. I have old computer parts that are stored in the basement waiting to be sold out for scrap metal or reused by electronics or computer students.

Speaking of scrap metal, I will try going to the junk yard and request the owner if I can put my hard disk under the big magnet that loads the metals onto the train cars. I will test if that kind of electromagnet can erase or destroy the data inside the hard disk. Sounds like mythbusters for me.

Too bad the sledge hammer is not an option. It's such a wonderful multipurpose tool and relieves stress too! ;)

Well, as continuum and I suggest, I think dban would be the best option for you. Recovering from a full dban pass will be incredibly hard, if possible at all. And will leave the disk reusable and in fine condition.

Anything you would want to try with magnets or other form of outside influence would almost certainly render the disk itself impaired and not re-usable anymore.

So look at it like this :

The data has to be gone forever, whatever happens : Dban it, thrash it and then burn it. Actually MELT the platters of the disk, only way to be sure

The data has to be gone 99,99% certainty, but I wish to re-use the device : Run a full Dban on it.

Actually submitting this to mythbusters would not be a bad idea. See if they can recover from a hammerd disk, or one that is frozen, dunked under watter, etc. etc. :P

Edited by Quindor

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The data has to be gone 99,99% certainty, but I wish to re-use the device : Run a full Dban on it.
Hell, it's more like 99.999999999% certain. I have the estimates from OnTrack to prove it-- they have yet to be able to recover a single one, even if it was a simple complete file overwrite rather than the much more through DBAN or even a basic Mil-spec overwrite.

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This has really been educational to read. I actually have a couple of old hard drives, out of the computer, that I just keep holding on to because I don't want someone to pick it up and get what is on it. Now this gives me something to look into so that I can get rid of them. Thanks.

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What does DBAN do that it totally deletes the files in the hard disk?

Quindor talked about placing the hard disk in the water. What damages will it do to the hard disk when it is sunk underwater?

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From a practical standpoint, just use DBAN and be done with. I'm sure it's theoretically possible for someone to glean some tiny bit of data from a disk post-DBAN, but it's not going to be worth anyone's time and energy.

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Cool article about the data recovery from a 6 months dunked disk! Sadly, my comment about the effect of water on a disk was taken a bit too seriously. I meant that as a test the Mythbusters could try, to see what the effect on the disk would be. Off course a running disk would short it's electronics, but the platters inside should be relatively safe. And thus data will remain obtainable.

I repeat my statement before. If you wish to have it 100% destroyed, slam the disk with a hammer till the top is loose, throw it into a fire and melt the magnetical disks inside. Your data is gone, for good. If you do not want to physically destroy your drive and re-use it. DBAN is your best choice.

All the other recovery tracks Ontrack talks about have all been physically damaged disks. No erased or rather, securely (DBAN) erased disks. So recovering from that will most likely be hard indeed. It's what I also believe, because of the process it uses.

There is also a pretty decent review over here, which explains a bit more. The standards you can use, which US military standards they are based on, etc. etc. very decent stuff.

Personally I always use the autonuke, I believe that writes a pass of 0's, then a pass of 1's and then a pass of 0's again. DBAN also does not look at partitions, or anything else on your disks, but uses lower level commands to just start at sector 0 till the end.

Found another interesting thread. Basically they say a single pass wipe should be more then enough, "autonuke" is a 3 pass process, more then enough for almost any usage case. And if you are not sure about it, you could use the 35 wipe pass method, from which even the author thinks it's complete overkill... :P

Edited by Quindor

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What does DBAN do that it totally deletes the files in the hard disk?

The ATA command set includes some commands that speed up the process of doing a secure erase (ok, not quite, but close). DBAN makes use of them to improve performance, meanwhile the overwrite methods are pretty standard.

http://en.wikipedia.org/wiki/DBAN

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Hi,

I think that magnets are not good to destroying data.. maybe for domestic use. From my experiences, I say that the best way is using professional degausser. I tried two types, both of them generated magnetic field destroying your data. One of them has innovative PPMS technology (Pre-Paid Management System). Pretty good one!

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Someday I will take one of my old working drives and test it on my induction coil with 24 kilojoules fed into it and see what happens. If that doesn't do it....

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Someday I will take one of my old working drives and test it on my induction coil with 24 kilojoules fed into it and see what happens. If that doesn't do it....

Now that's cool. Never built anything that large for the smaller projectile accelerator I put together years ago, had some issues with the photocell triggers and spacing. Looks like a fun project. and yes, I /think/ that will do a pretty good job of erasing data, or welding it if all else fails. :P

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If your aim is to make your data unreadable for old / failed drives, I use the following stages:

1) if the drive is still readable, use shred under Linux - just pop the drive in an eSATA caddy and set it running.

2) Using torx screwdriverss, remove the PCB and physically destroy it. Even if stage (1) can't be done, only somebody very dedicated will take a working drive and find the correct PCB to recover your data.

3) If time allows, and the disk wasn't already using an encrypted filesystem (I sometimes use LUKS on Debian), now open up the drives and scratch the platters with a screwdriver.

4) I never resort to this bit, but I've known people now smash the platters with a hammer (to satisfy client data destruction requirements).

Generally stage (2) only takes seconds and is a pretty good way to protect data on a failed drive.

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Hi,

I think that magnets are not good to destroying data.. maybe for domestic use. From my experiences, I say that the best way is using professional degausser. I tried two types, both of them generated magnetic field destroying your data. One of them has innovative PPMS technology (Pre-Paid Management System). Pretty good one!

Do you mead ProDevice deagusser? I have heard only about Garner's degaussers, by they don't have pre-paid functionality....

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