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

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

Turritopsis Dohrnii Teo En Ming-3
Good evening from Singapore!

The foremost question which I want to ask is, what is the universal
(world wide) understanding behind degaussing hard drives?

I work for No Secrets Agency (NSA) Pte Ltd (fictitious company name
used). My sales manager Edward Joseph Snowden (fictitious individual
name used) had *promised* our customer Leave Me in the Lurch (S) Pte
Ltd (fictitious company name used) that we would "DEGAUSS" their hard
disks after the PC replacement and data migration exercise for 15
trillion PCs (fictitious number used).

PC = Personal Computer, which includes desktops and laptops

Last Friday, I had already reflected to my sales manager Edward
Snowden that since we are definitely NOT going to wipe our customer's
data by using strong and powerful magnets (physical means), should I
send an email to the IT Administrator of our customer Lady Gaga
(fictitious individual name used) asking her which data sanitization
method (by software means) I should use? My sales manager Edward
Snowden had quickly deflected my concerns (that is, wanting to send an
email to our customer Lady Gaga asking her which data sanitization
method I should use).

I had brought up to the sales manager Edward Snowden a number of data
wiping methods by software means last Friday.

(1) Very very simple 1-pass data wiping, quickest

a. Using "sudo dd if=/dev/zero of=/dev/sda", overwriting harddisks
from beginning to end with zeroes, where /dev/sda refers to the 500 GB
harddisk, not /dev/loop0 and not /dev/sdb which refers to the bootable
live operating system on thumb drive

b. Using "sudo dd if=/dev/urandom of=/dev/sda", overwriting harddisks
from beginning to end with random data, where /dev/sda refers to the
500 GB harddisk, not /dev/loop0 and not /dev/sdb which refers to the
bootable live operating system on thumb drive

Any bootable Live CD/DVD/flash media could do it.

(2) 3-pass U.S. Government/Department of Defense (DoD) standard (DoD 5220.22-M)

Certified commercial software required

(3) 7-pass U.S. Government/Department of Defense (DoD) standard (DoD 5220.22-M)

Certified commercial software required

(4) 35-pass Gutmann method, slowest

Certified commercial software required

All these was last Friday. In the midst of our argument over the
cellular network "just now", my sales manager Edward Snowden tried to
cover up himself by suddenly and unexpectedly making an excuse that he
had told me last Friday I was supposed to wipe user data only, not the
operating system!

If he had wanted me to wipe user data and retain/keep the Windows
operating system, he should simply have told me to Reset the PC (for
Windows 10 only) or use a =secure File Shredder=! For Windows 7, you
can still wipe user data and preserve the operating system by using
the Recovery Partition. On Lenovo desktops, press and hold F11 when
Windows 7 is starting and reset to factory defaults.

I had advised my sales manager Edward Snowden not to use BIG WORDS
like "degaussing the harddisk" and market to the customer using these
big words. Any person who sees the word "degauss" would have
understood it to mean sanitize *ALL* data on the harddisk straight
away and without question.

Please refer to Figure 1. Exhibit A below for the "degaussing"
instructions communicated to me by my sales manager Edward Snowden.
Please click the link below.

URI: https://i.imgur.com/bGOMyVs.png

Please advise.

Thank you very much.

Regards,

Mr. Turritopsis Dohrnii Teo En Ming
Systems and Network Engineer
Republic of Singapore
2nd April 2018 Monday 9:35 PM Singapore Time GMT+8

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

Ralf Mardorf-2
On Mon, 2 Apr 2018 21:57:48 +0800, Teo En Ming wrote:
>Please advise.

For Zoho accounts my advice is to chose "Settings" > "Filters" and than
to add the rule "Sender is [hidden email]" "Delete Yes".

That is what I've done.



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

Ken D'Ambrosio
On 2018-04-02 10:25, Ralf Mardorf wrote:
> On Mon, 2 Apr 2018 21:57:48 +0800, Teo En Ming wrote:
>> Please advise.
>
> For Zoho accounts my advice is to chose "Settings" > "Filters" and than
> to add the rule "Sender is [hidden email]" "Delete Yes".
>
> That is what I've done.

1) Alas, those instructions don't work for Roundcube. ;-)

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.

$.02,

-Ken

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

Tommy Trussell

On Mon, Apr 2, 2018 at 9:34 AM, Ken D'Ambrosio <[hidden email]> 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.)

 

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

Wynona Stacy Lockwood
On Tue, Apr 3, 2018 at 11:06 AM, Tommy Trussell <[hidden email]> wrote:

On Mon, Apr 2, 2018 at 9:34 AM, Ken D'Ambrosio <[hidden email]> 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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Re: What is the universal (world wide) understanding behind degaussing harddisks?

Ralf Mardorf-2
In reply to this post by Tommy Trussell
On Tue, 3 Apr 2018 11:06:26 -0500, Tommy Trussell wrote:
>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'm an old audio and video engineer. I don't own this huge thingy to
degauss old PAL tube TV sets, when they start to display colours like
"Never Twice the Same Color" television sets from other countries, but
I still own a degausser for analog tape head and capstan. I guess it
could harm data on a HDD, but I seriously doubt that it is able to
completely remove data from a HDD. The solid metal casing of a HDD more
likely could damage a degausser.


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

Ralf Mardorf-2
On Tue, 3 Apr 2018 18:36:38 +0200, Ralf Mardorf wrote:

>On Tue, 3 Apr 2018 11:06:26 -0500, Tommy Trussell wrote:
>>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'm an old audio and video engineer. I don't own this huge thingy to
>degauss old PAL tube TV sets, when they start to display colours like
>"Never Twice the Same Color" television sets from other countries, but
>I still own a degausser for analog tape head and capstan. I guess it
>could harm data on a HDD, but I seriously doubt that it is able to
>completely remove data from a HDD. The solid metal casing of a HDD more
>likely could damage a degausser.

Sorry for the German qoute [1].

At room temperature iron, nickel and cobalt interact with the degausser.

The German quote mentions an "Edelstahl-Blechdeckel" for HDDs, so this
could be a serious issue for the degausser.

[1]
"Festplatten-Gehäuse

Das Gehäuse einer Festplatte ist sehr massiv. Meist ist es ein aus
einer Aluminiumlegierung bestehendes Gussteil und mit einem
Edelstahl-Blechdeckel versehen." -
https://de.wikipedia.org/wiki/Festplattenlaufwerk#Festplatten-Geh%C3%A4use


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

Ralf Mardorf-2
As other alredy pointed out, first use the sledgehammer and after
that use cement shoes in the middle of the ocean.


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

David Fletcher-5
In reply to this post by Tommy Trussell
On Tue, 2018-04-03 at 11:06 -0500, Tommy Trussell wrote:
> 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.)

There's a pair of impressively powerful little magnets that I believe
are part of the head positioning mechanism, so if a drive were to be
totally degaussed the drive would indeed be toast.

BTW I once tried to degauss some DAT tapes with all sorts of gadgets,
to re-use them in another drive (as I recall the drives appear to write
their own "signature" on the tape so they won't work in another one so
no use for disaster recovery after e.g. a fire). The only machine that
did it was one that I found on an industrial estate where they
manufactured large custom magnets, the final stage being to put them in
this machine that as I recall dumped a large capacitor bank into an
electromagnet. That wiped the DAT tapes. I strongly suspect that the
magnetic domains on hard drives, tapes and things are not as delicate
as some would have us believe.

Dave

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

David Fletcher-5
PS

I always use a lump hammer to drive a cold chisel through any drive I
intend to put in the metal recycling bin.


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