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Author Topic: Hard drives and magnets
Goombah
I'll Be Home for After Christmas Sales


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I was prepping my dearly departed laptop for the recycler when a friend of mine and his late teenage son stopped by my shop. I had just extracted the hard drive from the laptop and was getting ready to destroy it by running it through the drill press a few times. When asked, I explained that the computer was toast and that I wanted to make sure none of the personal info on the hard drive fell into the wrong hands. The boy asked if he could have the drive to upgrade his own laptop. I had no use for it and I do believe in recycling so I said sure as long as I could make sure my data was safe. His computer was three states away so we couldn't use it to wipe my drive and I had no other way of accomplishing this.

I pondered this briefly before I had the "brilliant" idea to take the HD with me to work and run it through the degausser. That might do the trick. The degausser is basicly just a big doughnut shaped electromagnet about 18" across and running on 440 volts. Flip it on, pass a ferrous object through it a few times, boom, no more magnetic charge. I don't know how strong the field strength is but my own testing proves that it's more than strong enough to wipe an old Tone-Loc cassette.

After I did this (of course) I asked my computer savy friend and he said I probably fried the HD. The data is suitably scrambled but now its just a 20 gig paperweight that will never work again. How likely is this to be true? Did I just destroy a perfectly useable drive? Conversely, is it possible that the drive and data are completely intact? I don't have access to any working laptop so that I can test this.

What should I do? Do I give the drive to the boy and hope for the best? Do I just destroy it and say "Better luck next time!"?

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Ok guys, try to remember this time. It's pillage first, then burn.

Posts: 179 | From: Holdrege, NE | Registered: Jan 2006  |  IP: Logged | Report this post to a moderator
Not_Done_Living
I'm Dreaming of a White Sale


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You may have caused head damage, which is the read/write arm and which is extremely delicate. If it touches the platter... thats a bad thing

Also. if the Magnet is strong enough and causes the platters to shift.. that may also be a bad thing...

Most likely though.. he just needs to repartition the drive and install his OS.

Worse comes to worse.. you KNOW your data is safe and his kid doesn't get the free hard drive that he didn't have previously, PLUS you have found a better/safer way to destroy your old data sensitive devices without the risk of flying metal/porcelain [Smile]

Posts: 62 | From: Markham, Ontario, Canada | Registered: Sep 2006  |  IP: Logged | Report this post to a moderator
WildaBeast
Let There Be PCs on Earth


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I don't know how strong a magnetic field the degausser produces, but using a big magnet is exactly how the IT department at work wipes the hard drives on old laptops before they resell/donate them. Just based on that I'd think it's probably fine.

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"Unseasonable is an odd word to begin with. It sounds like it's describing something that it's impossible to sprinkle pepper on." -- Nonny

Posts: 5483 | From: Just south of Folsom Prison, CA | Registered: Jul 2002  |  IP: Logged | Report this post to a moderator
Orpheus
I'm Dreaming of a White Sale


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You can't erase a hard disk with a magnet unless you open it and bring the magnet very close to the platters. This will have two effects:

1) It will destroy the drive, because opening a hard disk kills it immediately (unless done in a cleanroom).

2) It will destroy the drive, because wiping the information off the platters also wipes off the guidance tracks used to position the read/write heads.

The most likely outcome of your degausser is nothing. On the bright side, it's more effective than a standard magnet because of the alternating field.

WildaBeast: I'd suggest getting your IT department to test the disks after they've been wiped.

Posts: 5 | From: Perth, WA | Registered: Sep 2006  |  IP: Logged | Report this post to a moderator
chillas
Coventry Mall Carol


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Degaussers are commonly used for safe hard drive disposal. They are quite effective, but in all probability will damage the drive beyond use.

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Come on, come on - spin a little tighter
Come on, come on - and the world's a little brighter


Posts: 5595 | From: Columbus, OH : The Soccer Capital of America | Registered: Sep 2002  |  IP: Logged | Report this post to a moderator
abigsmurf
We Wish You a Merry Giftmas


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be warned, drilling a hdd doesn't make data unrecoverable. Good forensics can still extract pieces of data from it, it's just very difficult, expensive and only produces fragments of info.

I'm not sure what sort of error correction a hdd uses but a CD could still play if a hole is drilled in it because of the error correction.

Posts: 824 | From: England | Registered: Mar 2005  |  IP: Logged | Report this post to a moderator
Troberg
Angels Wii Have Heard on High


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It depends. If the degausser is running an alternating magnetiv field, it will probably work, otherwise not. The problem is that you will most likely eff up the low level format, and nowadays the BIOS usually can't do that, effectively killing the disk. Also, the data could probably be read by companies and organizations with specialist equipment, which may or may not be a problem for you.

My advise for hard drive disposal:

* If drive is to be thrown away
Put it on an anvil and give it all you got with a heavy sledge hammer. Organizations with strict needs for secrecy, such as military or health care, usually use a machine which chew it up into fine metal flakes, but I think the sledge hammer is a workable alternative for most uses.

* If you want to use the drive
Reformat it. Fill it with random data. Repeat 25 times (15 times is said to be the maximum overwritings that data can be retrieved from by the leading intelligence agencies, so 25 should be enough). There is software that does this for you.

* If you want to use the drive and just want to make sure it can't be read without special equipment
Format it. No quick format, do a real format. It can't be read without removing the physical disks from the hard drive and putting it in a special reading mechanism.

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/Troberg

Posts: 4360 | From: Borlänge, Sweden | Registered: Nov 2005  |  IP: Logged | Report this post to a moderator
Eddylizard
We Wish You a Merry Giftmas


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quote:
Originally posted by abigsmurf:
be warned, drilling a hdd doesn't make data unrecoverable. Good forensics can still extract pieces of data from it, it's just very difficult, expensive and only produces fragments of info.

I'm not sure what sort of error correction a hdd uses but a CD could still play if a hole is drilled in it because of the error correction.

I suppose it really comes down to how sensitive the data is, and how paranoid you are about data recovery.

If anyone hacked my hard drive, they'd find a few cr*p stories I'd written, and some passwords for free to enter sites. I'd have no problem with a one pass wipe.

On the other hand, If I had a spreadsheet detailing the next six months shipments of Bolivian Marching Powder from contacts in Colombia, then I might take a few more precautions.

So the level of precaution has to be reasonable with regard to with the level of sensitivity.

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"Ladies and gentlemen, this is what is commonly known as money. It comes in all sizes, colours, and denominations - like people."

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Singing in the Drizzle
Jingle Bell Hock


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If I was just giving the HD to a friend and I know there is nothing sensitve then I download a free diskwipe program. These will erease the HD and fill with random 1 & 0's.

If the HD is going in the garbage. Open it up if I can and destrory the disks. If I can't get it open, then its the sledge hammer.

Posts: 597 | From: Bellingham, WA | Registered: Nov 2005  |  IP: Logged | Report this post to a moderator
Goombah
I'll Be Home for After Christmas Sales


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First of all, many thanks for the kind replies. [Smile]

I am somewhat paranoid about recovered data. I'm not saying that paranoia is justified but that's the way it is. I've got a couple of credit card numbers on there along with a few other tidbits of personal data. I'm not all that worried about the police or FBI dissecting the drive for my porn secrets but I need to know that the typical hacker using software tools can't access the data. Since I have no way of verifying the disk status I've just decided to destroy the HD and let Junior find his free upgrade elsewhere. It's now been drilled several times and crushed in a vice.

Troberg
quote:
* If you want to use the drive
Reformat it. Fill it with random data. Repeat 25 times (15 times is said to be the maximum overwritings that data can be retrieved from by the leading intelligence agencies, so 25 should be enough). There is software that does this for you.

What free software is available for this purpose? It wouldn't have been useful for me in this case since my laptop died without giving me the opportunity to wipe the drive but I'd like the software for future use.

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Ok guys, try to remember this time. It's pillage first, then burn.

Posts: 179 | From: Holdrege, NE | Registered: Jan 2006  |  IP: Logged | Report this post to a moderator
Troberg
Angels Wii Have Heard on High


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There was a program called Discreet (or perhaps Diskreet) around, but it's a few years since I used it. I think I've seen one called DiscWipe or something like that.

Remember, in most cases you have to run it from a bootable disk, as you are actually wiping the disk you are otherwise starting from. That's both good and bad. It's a little extra job, but it can be done even if the computer is quite effed up.

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/Troberg

Posts: 4360 | From: Borlänge, Sweden | Registered: Nov 2005  |  IP: Logged | Report this post to a moderator
chillas
Coventry Mall Carol


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Eraser

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Come on, come on - spin a little tighter
Come on, come on - and the world's a little brighter


Posts: 5595 | From: Columbus, OH : The Soccer Capital of America | Registered: Sep 2002  |  IP: Logged | Report this post to a moderator
   

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