Zeroing Hard Drives

[ExXB]

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 ???

[dsc810]

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.

[ExXB]

yes, but how can they read anything other than zeros? Or is the zero out just random sectors rather than everything?

[Saab Dastard]

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

[MG23]

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.

But also a heck of a job; I've done it myself a couple of times, and disks are hard to destroy unless you have a sledgehammer handy. If i remember correctly, the approved 'military wipe' specification for the systems a friend worked on in the 90s was a thermite charge, or a full magazine from an M-16.

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?

[boguing]

Take them apart. The discs make excellent shaving mirrors.

[ShyTorque]

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.

[ExXB]

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.

Describes this situation perfectly. But to be even more safe I did the 'single pass' option twice. :ok:

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)?? :hmm:

[Capn Bloggs]

You lot obviously don't chop wood (is wood-burning banned by the PC European Commission??). The blunt side of an axe works perfectly and VERY therapeutic!

[dazdaz1]

In the past I've placed the hd on the gas ring (low flame) and leave for about 10 minutes. End result the hd resembles a papadom, distorted bubbled and data has gone forever.

[Ancient Observer]

Another vote from me for Therapeutic destruction. Hammer, axe, and very heavy duty clippers work a treat. And the exercise.............and it makes you warm.........

[Midland 331]

https://flic.kr/p/bWFQvW

Done!

[Capot]

An angle grinder worked for me, but it was quite a long job and used more than one cutter disc. It was replaced by two SSDs that I could interchange (Work and Play) and I never looked back.

[Midland 331]

>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.

[Mr Optimistic]

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?