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


On Tue, Apr 3, 2018 at 11:06 AM, Tommy Trussell <tommy.trussell at gmail.com>
wrote:

>
> On Mon, Apr 2, 2018 at 9:34 AM, Ken D'Ambrosio <ken at jots.org> wrote:
>
>>
>> 2) I dunno -- it was pretty damn long-winded, but seemed above-board.
>> Me?  I've *never* seen convincing proof that anything could be recovered
>> from a drive that's been completely overwritten once with *anything*.  I'm
>> sure the DOD, etc., use crazy overwrite schemes, but the tolerances are
>> already vanishingly small just to store the data, much less recover
>> overwritten data.  Not saying it's impossible, but unless you're worried
>> about the NSA, I'm thinking "one pass and done" is the answer.  Almost
>> certainly preferable to actual degaussing, as that likely *would* leave
>> remnant bits, unless you just completely overwhelm it.  Which is likely
>> beyond the means of old degaussing rings used for fixing CRTs and the like.
>>
>
> If someone told me to "degauss" a hard drive, I would NOT suggest any
> software to do it, because it's not technically possible. Degaussers
> (attempt to) ELIMINATE residual magnetic fields. Hard drive heads CREATE
> magnetic fields in tiny spots on the platters, and in fact the drive
> DEPENDS upon the existence of magnetized regions to operate. Unless there's
> a paranoid drive containing a built-in self-destruct feature, I believe it
> is not possible tell a drive to remove ALL magnetic fields from the
> platters, which is what a "degausser" would do.
>
> In my (very limited) experience, one can use an "old fashioned" tape
> "degausser" aka "demagnetizer" on a hard disk, but after doing so the drive
> is generally "toast." (I suspect the head mechanism gets damaged by the
> process, and the motors probably don't take kindly to being degaussed
> either.) SO it would be impossible to determine whether residual data could
> be retrieved from a degaussed drive without taking it apart and examining
> the platters in the same manner as a data recovery service might do.
>
> I suggest that a more time-efficient way to prevent access to information
> on a hard drive is by putting it through a metal shredder.
>
> For most purposes I would suggest a very strong magnet or degausser
> followed by the judicious application of a drill or heavy hammer to the
> platters might be sufficiently secure, but I am probably not paranoid
> enough.
>
> (As I write this I recall a storage shelf containing dozens of old drives
> dating back decades that I haven't even taken the time to reformat.)
>
>
Drive shredders can be rented on the cheap. If you aim to ensure that there
is no chance that someone will read your old data when getting rid of a
drive, physical destruction is really the only option. Secure wipes are ok
for anything not mission critical, but anything that is mission critical or
contains intellectual property that you should protect, I always suggest
using a drive shredder.

Of course, if you're a home user with no such considerations, a single pass
wipe or even just a plain old reformat is likely good enough.
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