Disk Wiping Test: Testing and other FAQs

Shredded test CDs How did you test?

  1. Restored a Ghost image of Windows XP to laptop with a 120GB hard drive.
  2. Copied 24919 files onto the laptop C: drive.
    (1955MB in total)
  3. Shutdown laptop
  4. Booted with the ““KillDisk”” and run the utility.

And the restore test?
Booted the laptop with TestDisk & PhotoRec, and ran those to try and restore the data.

How many products did you test?
I tried testing 8 products.  Some were so bad, I didn’t do a full test/write-up.

Why only one pass wipe (with some products)?
Because that is all you need.
They concluded that, after a single overwrite of the data on a drive, whether it be an old 1-gigabyte disk or a current model (at the time of the study), the likelihood of still being able to reconstruct anything is practically zero. Well, OK, not quite: a single bit whose precise location is known can in fact be correctly reconstructed with 56 per cent probability (in one of the quoted examples). To recover a byte, however, correct head positioning would have to be precisely repeated eight times, and the probability of that is only 0.97 per cent. Recovering anything beyond a single byte is even less likely.”

What is ATA Secure Erase?
A command which tells your hard drive to wipe itself.  Most ATA/SATA drives have supported this command since 2001.  Not all Disk Wiping programs support it.
It would seem to be the most secure way to wipe a hard disk.
Further information here.

What are the other wipe (software) techniques?
Peter Gutmann’s
3-pass US DoD 5220-22M
One-pass random
German VSITR standard
Bruce Schneier’s:
”I recommend overwriting a deleted file seven times: the first time with all ones, the second time with all zeros, and five times with a cryptographically secure pseudo-random sequence.”
“Applied Cryptography” (1996)

What about hardware devices?
Didn’t test any hardware wiping devices, but I’ve got some experience with them, so here are some general comments.

Degaussers – destructive wiping.
sv91m degausser These kinds of devices work so well that they bend parts of the hard drive.
Yes, your drive is wiped, but it will never work again.

Hardware based wiping devices

Hardware drive destroyers
Exactly what the title said, via crushing, shredding or disintegrating.

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