Zeroing Hard Drives
Thread Starter
Joined: May 2009
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From: Confoederatio Helvetica
Zeroing Hard Drives
Have a couple of old Hard Drives that I want to dispose of. So, using my Mac's disc utilities I see I have four options:
1. Erases just the File allocation information. Data could be gotten to by just about anyone (and their dog)
2. Writes, in one pass, a zero over every bit of the disk.
3. Writes, in a few passes, zeros etc.
4. Meets DoD specifications and writes zeros seven times (etc.)
Obviously number 1 isn't what I want.
But what is the difference between Number 2 and Number 4. Why would seven passes be better than one. A zero is a zero - my data should be nuked.
The difference in time for a 150gb disk is about six hours.
Do I really need to leave this overnight ???
1. Erases just the File allocation information. Data could be gotten to by just about anyone (and their dog)
2. Writes, in one pass, a zero over every bit of the disk.
3. Writes, in a few passes, zeros etc.
4. Meets DoD specifications and writes zeros seven times (etc.)
Obviously number 1 isn't what I want.
But what is the difference between Number 2 and Number 4. Why would seven passes be better than one. A zero is a zero - my data should be nuked.
The difference in time for a 150gb disk is about six hours.
Do I really need to leave this overnight ???
Joined: Aug 2008
Posts: 3
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From: UK
Because it is possible with some really decent kit to read what was there before the previous overwrites occurred: hence the multiple passes.
This certainly applies to standard rotating hard drives
no idea if it possible with SSD's - ask GCHQ.
I'd take it outside and attack it a sledge hammer and smash the platters.
Which is probably one down from an ultra secure erasure which is where the magnetic material is sand blasted off the platters.
This certainly applies to standard rotating hard drives
no idea if it possible with SSD's - ask GCHQ.
I'd take it outside and attack it a sledge hammer and smash the platters.
Which is probably one down from an ultra secure erasure which is where the magnetic material is sand blasted off the platters.
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From: Twickenham, home of rugby
The requirement to have multiple passes of writing zeros and / or random data to securely erase a HDD is largely gone.
15-20 years ago, the areal densities of HDDs were such that it might - by using highly sophisticated tools - have been possible to extract meaningful amounts of data from a disk erased with a single pass of zeros.
It's simply not feasible to recover more than a tiny fraction of bits on today's HDDs, and that is insufficient to extract actual data.
So one pass is fine for most situations where the potential value of any recovered data is far, far less than the cost to attempt to extract it.
And if you want to render the disk truly useless, dismantle it and shred / smash the platters to smithereens, which has the side effect of being rather therapeutic.
SD
15-20 years ago, the areal densities of HDDs were such that it might - by using highly sophisticated tools - have been possible to extract meaningful amounts of data from a disk erased with a single pass of zeros.
It's simply not feasible to recover more than a tiny fraction of bits on today's HDDs, and that is insufficient to extract actual data.
So one pass is fine for most situations where the potential value of any recovered data is far, far less than the cost to attempt to extract it.
And if you want to render the disk truly useless, dismantle it and shred / smash the platters to smithereens, which has the side effect of being rather therapeutic.
SD
Joined: Jun 2009
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From: Canada
The best method these days is the one most modern SSDs use; they have an internal encryption key they use to encrypt everything written to the disk. Then they have a 'secure wipe' command which tells the disk to throw away the old encryption key and generate a new one. Any remaining data is completely useless at that point, because you'd have to be able to break 256-bit AES encryption to read it. Wonder if modern hard drives do the same?
Avoid imitations
Joined: Nov 2000
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From: Wandering the FIR and cyberspace often at highly unsociable times
Heating a magnet reduces its strength. Heat the platters enough and they will no longer be magnetic. Taking the thing apart and blow lamping the platters is less messy than a big hammer.
I also keep the magnets for various uses.
I also keep the magnets for various uses.
Thread Starter
Joined: May 2009
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From: Confoederatio Helvetica
So one pass is fine for most situations where the potential value of any recovered data is far, far less than the cost to attempt to extract it.
A few years back I did destroy a HD manually. Broke one screwdriver and a claw hammer in the process. Hardly therapeutic!!! Worst part is you can't buy claw hammers here, and you can't bring them home in carry on!
Now does anyone want to buy a 40GB La Cie Hard drive, that is the size of bread box (almost)??
Joined: Jul 2005
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From: Teesside
Joined: Jul 2005
Posts: 512
Likes: 2
From: Teesside
>but it was quite a long job and used more than one cutter disc
?! What else were you cutting through?
1/ Remove cover (you may need a security / torx bit.
2/ Apply angle grinder as per photo. 30 seconds.
?! What else were you cutting through?
1/ Remove cover (you may need a security / torx bit.
2/ Apply angle grinder as per photo. 30 seconds.
Joined: Jun 2009
Posts: 1,344
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From: Bedford, UK
Yes just unscrew it and then score the disc with tool of choice. Unless you are of interest to the CIA that should do it. Hitting the whole thing with the hammer side of a splitting axe also works and makes for a nice tinkling noise. No idea how it could take very long...more spinach?
