What is the universal (world wide) understanding behind degaussing harddisks?

Colin Faber cfaber at gmail.com
Mon Apr 2 16:47:16 UTC 2018


shred with random write 3 pass and zero'd forth pass should be enough for
most data recovery efforts. SSDs however are another problem, as they're
copy on write devices and are over provisioned to accommodate for failure.
In those cases I would consider 9 to 16 full disk random writes with at
least 4 zeroing passes, but that still doesn't guarantee the data will not
be recoverable.

On Mon, Apr 2, 2018, 10:00 AM Diane Bruce <db at db.net> wrote:

> On Mon, Apr 02, 2018 at 09:46:05PM +0800, Turritopsis Dohrnii Teo En Ming
> wrote:
> > Good evening from Singapore!
> >
> > The foremost question which I want to ask is, what is the universal
> > (world wide) understanding behind degaussing hard drives?
> If you degauss a modern drive you will make it totally useless to
> use. You might as well quarter the drive with a bandsaw and incinerate.
> (This was the recommended procedure for security disks from a
> (fictitious) agency I worked (indirectly) for years ago.)
> The problem is modern drives lay down servo tracks on the platters
> which can only be done at the factory.
> >
> > (1) Very very simple 1-pass data wiping, quickest
> >
> > a. Using "sudo dd if=/dev/zero of=/dev/sda", overwriting harddisks
> ...
> >
> > b. Using "sudo dd if=/dev/urandom of=/dev/sda", overwriting harddisks
> Any method you use will *not* remove all data due to the slight wobble
> of the track due to temperature changes in the disk, vibration all sorts
> of problems. However at that point if done properly it would take
> specialized gear only (fictitious) security agencies such as the NSA
> (fictitious company) would be likely to bother with.
> The TL;DR answer is. If you want to use the drives afterwards don't
> simply demagnetize them; A triple write is probably sufficient if it is
> merely company data. if the data is drug dealings or state secrets
> then destroy the drives.   ;)
> > Mr. Turritopsis Dohrnii Teo En Ming
> > Systems and Network Engineer
> > Republic of Singapore
> > 2nd April 2018 Monday 9:35 PM Singapore Time GMT+8
> --
> - db at FreeBSD.org db at db.net http://www.db.net/~db
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