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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 <tdteoenming@gmail.com> - 2018-04-02 15:50 +0200
    Re: What is the universal (world wide) understanding behind  degaussing harddisks? Roberto C. Sánchez <roberto@debian.org> - 2018-04-02 16:10 +0200
      Re: What is the universal (world wide) understanding behind  degaussing harddisks? Ben Caradoc-Davies <ben@transient.nz> - 2018-04-02 23:30 +0200
    Re: What is the universal (world wide) understanding behind  degaussing harddisks? Michael Stone <mstone@debian.org> - 2018-04-02 17:50 +0200
      Re: What is the universal (world wide) understanding behind degaussing harddisks? John Hasler <jhasler@newsguy.com> - 2018-04-02 18:30 +0200
        Re: What is the universal (world wide) understanding behind  degaussing harddisks? Curt <curty@free.fr> - 2018-04-02 19:20 +0200
          Re: What is the universal (world wide) understanding behind  degaussing harddisks? Michael Stone <mstone@debian.org> - 2018-04-02 19:30 +0200
          Re: What is the universal (world wide) understanding behind degaussing harddisks? John Hasler <jhasler@newsguy.com> - 2018-04-02 20:10 +0200
            Re: What is the universal (world wide) understanding behind  degaussing harddisks? David Wright <deblis@lionunicorn.co.uk> - 2018-04-03 17:20 +0200
              Re: What is the universal (world wide) understanding behind   degaussing harddisks? Dan Purgert <dan@djph.net> - 2018-04-03 18:00 +0200
        Re: What is the universal (world wide) understanding behind  degaussing harddisks? Michael Stone <mstone@debian.org> - 2018-04-02 19:30 +0200
          Re: What is the universal (world wide) understanding behind degaussing harddisks? John Hasler <jhasler@newsguy.com> - 2018-04-02 21:50 +0200
    Re: What is the universal (world wide) understanding behind degaussing harddisks? rhkramer@gmail.com - 2018-04-02 19:40 +0200

#194398 — What is the universal (world wide) understanding behind degaussing harddisks?

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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#194400 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

On Mon, Apr 02, 2018 at 09:40:40PM +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?
> 
[Snip long and entertaining problem description]
> 
> Please advise.
> 
My preference is to first thoroughly shred the device (for traditional
spinning disk, as these utilities are not especially effective on solid
state media thanks to write leveling):

sudo shred -n 37 -v -z /dev/sda
(or alternatively, boot a DBAN disk and use its wipe function)

Then, if it has ATA secure erase (hdparm -I /dev/sda | grep -i erase), I
also wipe it like so:

hdparm --security-set-pass password /dev/sda
hdparm --security-erase-enhanced password /dev/sda

It is necessary to first set the password, assuming it has not
previously been set, or the drive will just return an error.

Also, the ATA enhanced erase is, as far as I know, the best option for
wiping an SSD. Assuming, that is, that you do not want to physically
shred/pulverize the device.

As an interesting note, the enhanced erase takes on the order of ~3
*hours* for a decent sized (e.g., 2 TB) HDD, but on the order of ~3
*minutes* for an SSD of the same size.

Regards,

-Roberto

-- 
Roberto C. Sánchez

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#194421 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

On 03/04/18 02:08, Roberto C. Sánchez wrote:
> Also, the ATA enhanced erase is, as far as I know, the best option for
> wiping an SSD.

+1. It may also erase things like reserved space and bad blocks that are 
not visible via the block device and thus immune to shred.

ATA security erase is the facility provided by the manufacturer and I 
would tend to take their advice on how to securely erase their product. 
This should be sufficient for all commercial users. Paranoid national 
security users will require pulverisation of the physical media.

My preferred approach is to encrypt all content (e.g. LUKS) before 
writing to any media, to provide an additional layer of protection.

Kind regards,

-- 
Ben Caradoc-Davies <ben@transient.nz>
Director
Transient Software Limited <https://transient.nz/>
New Zealand

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#194402 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

Degaussing a hard drive will render it inoperative. It's also relatively 
hard to do/requires special equipment. (Just waving a refrigerator 
magnet around isn't going to do it.) Degaussing should be understood as 
a final step before discarding equipment. (And, for what it's worth, 
it's not a process I generally favor because it's hard to verify that 
the data on the disk has actually been erased; in most cases I'd 
recommend physical destruction over degaussing.)

Mike Stone

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#194404

Mike Stone writes:
> Degaussing a hard drive will render it inoperative. It's also
> relatively hard to do/requires special equipment. (Just waving a
> refrigerator magnet around isn't going to do it.)

The equipment required for degaussing isn't very special (though it
*does* require an AC magnet).  However, a determined opponent can
probably recover data from a degaussed disk.  Overwriting with zeros is
probably more effective with modern disks (the hard part may be making
sure every physical sector actually does get overwritten).

If the device contains truly sensitive and important data destroy it.
For ordinary people, though, an erase program is more than adequate.
Nobody cares enough about your secrets to make any kind of a serious
effort to recover them from a scrapped disk.
-- 
John Hasler 
jhasler@newsguy.com
Elmwood, WI USA

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#194406 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

On 2018-04-02, John Hasler <jhasler@newsguy.com> wrote:
> Mike Stone writes:
>> Degaussing a hard drive will render it inoperative. It's also
>> relatively hard to do/requires special equipment. (Just waving a
>> refrigerator magnet around isn't going to do it.)
>
> The equipment required for degaussing isn't very special (though it
> *does* require an AC magnet).  However, a determined opponent can
> probably recover data from a degaussed disk.  Overwriting with zeros is
> probably more effective with modern disks (the hard part may be making
> sure every physical sector actually does get overwritten).
>
> If the device contains truly sensitive and important data destroy it.
> For ordinary people, though, an erase program is more than adequate.
> Nobody cares enough about your secrets to make any kind of a serious
> effort to recover them from a scrapped disk.

I guess the only means of verifying whether your data has been
effectively destroyed is by attempting to recover it; as the
threat-scenarios spoken about here (by individuals) generally posit
attackers (corporate or governmental) with more resources at their
disposal than they have at theirs, this task proves to be more arduous
(if not nigh on impossible) than the destruction itself.

I took a hammer once to an old hard drive; frankly, I don't know whether
I killed it or not. But they don't call 'em "hard" drives for nothin',
I'll tell ya that.

That sucker was ornery. I pretty seriously dented it, is all of which
I'm certain.

-- 
The time-state of attainment eliminates so accurately the time-state of
aspiration, that the actual seems the inevitable, and, all conscious
intellectual effort to reconstitute the invisible and unthinkable as a reality
being fruitless, we are incapable of appreciating our joy by comparing it with
our sorrow.  --Samuel Beckett

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#194408 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

On Mon, Apr 02, 2018 at 05:10:41PM +0000, Curt wrote:
>I took a hammer once to an old hard drive; frankly, I don't know whether
>I killed it or not. But they don't call 'em "hard" drives for nothin',
>I'll tell ya that.

The hammer method is far more satisfying with glass platters. :)

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#194412

Curt writes:
> I guess the only means of verifying whether your data has been
> effectively destroyed is by attempting to recover it; as the
> threat-scenarios spoken about here (by individuals) generally posit
> attackers (corporate or governmental) with more resources at their
> disposal than they have at theirs...

You also must posit the data being valuable enough to such opponents for
them to be willing to *spend* that much to get it.  I'm quite confident
that none of mine is.

> ...this task proves to be more arduous (if not nigh on impossible)
> than the destruction itself.

Heating the disks to well above the Curie point of the magnetic coating
is guaranteed to destroy all the data.  That's much easier than running
it through a National Magnet Lab sized magnet, especially since if they
are aluminum they will melt.  Glass ones are easily smashed, of course.

> I took a hammer once to an old hard drive; frankly, I don't know whether
> I killed it or not. But they don't call 'em "hard" drives for nothin',
> I'll tell ya that.

> That sucker was ornery. I pretty seriously dented it, is all of which
> I'm certain.

The cases come apart quite easily and yield useful parts such as
rare-earth magnets.  I'm quite certain that I could destroy one with a
ten-pound sledgehammer, though.
-- 
John Hasler 
jhasler@newsguy.com
Elmwood, WI USA

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#194451 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

On Mon 02 Apr 2018 at 13:07:48 (-0500), John Hasler wrote:
> Curt writes:
> > I guess the only means of verifying whether your data has been
> > effectively destroyed is by attempting to recover it; as the
> > threat-scenarios spoken about here (by individuals) generally posit
> > attackers (corporate or governmental) with more resources at their
> > disposal than they have at theirs...
> 
> You also must posit the data being valuable enough to such opponents for
> them to be willing to *spend* that much to get it.  I'm quite confident
> that none of mine is.

Agreed, but the OP is full of hypotheticals so we have to play along!

> > ...this task proves to be more arduous (if not nigh on impossible)
> > than the destruction itself.
> 
> Heating the disks to well above the Curie point of the magnetic coating
> is guaranteed to destroy all the data.

But how to determine what the curie point of the particular drives is
might be taxing. And the contents of disks have been recovered from
drives in buildings consumed by fire.

> The cases come apart quite easily and yield useful parts such as
> rare-earth magnets.  I'm quite certain that I could destroy one with a
> ten-pound sledgehammer, though.

Whatever the process is, it has to scale well if there are trillions
of drives. So I would agree with Ben that as usual, prevention is
better than cure: use LUKS from day one.

Cheers,
David.

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#194453 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

David Wright wrote:
> On Mon 02 Apr 2018 at 13:07:48 (-0500), John Hasler wrote:
>> Heating the disks to well above the Curie point of the magnetic coating
>> is guaranteed to destroy all the data.
>
> But how to determine what the curie point of the particular drives is
> might be taxing. And the contents of disks have been recovered from
> drives in buildings consumed by fire.

Not really. Toss into a crucible, wait until it has melted. In the event
the drives use "standard" ceramics, this is only about 1600 C (slightly
hotter than iron, slightly cooler than titanium)

Even your standard propane blowtorch will hit upwards of that
temperature in air.  Granted, you'd do better using a 2-gas propane +
oxygen (2800 C) or acetylene + oxygen (3100 C) setup.

-- 
|_|O|_| Registered Linux user #585947
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: 05CA 9A50 3F2E 1335 4DC5  4AEE 8E11 DDF3 1279 A281

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#194409 — Re: What is the universal (world wide) understanding behind degaussing harddisks?

On Mon, Apr 02, 2018 at 11:23:29AM -0500, John Hasler wrote:
>The equipment required for degaussing isn't very special (though it
>*does* require an AC magnet).

You need to match the strength of the equipment to the media in use. 
Modern hard disks need fairly strong fields to fully erase, and there's 
a lot of older equipment out there which simply won't work well because 
it was designed to erase older media.

>However, a determined opponent can
>probably recover data from a degaussed disk.

Not one that's properly degaussed. But, as I said, verification is 
difficult.

>Overwriting with zeros is
>probably more effective with modern disks (the hard part may be making
>sure every physical sector actually does get overwritten).

Overwriting with zeros is sufficient and effective for most purposes. 
The erase 7 times with patterns stuff is basically techie mumbo-jumbo. 
It can leave traces in non-writable parts of the disk, which the 
secure-erase commands attempt to address. The main reasons to look at 
degaussing or other methods of destruction are 1) for extremely 
sensitive data, 2) for drives which are broken (it's quite possible for 
something to be too broken to overwrite, but not too broken to extract 
data) or 3) because it's quicker/easier/cheaper to destroy a bunch of 
hard disks than to erase *and verify*.

Mike Stone

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#194420

Michael Stone writes:
> The main reasons to look at degaussing or other methods of destruction
> are 1) for extremely sensitive data, 2) for drives which are broken
> (it's quite possible for something to be too broken to overwrite, but
> not too broken to extract data) or 3) because it's
> quicker/easier/cheaper to destroy a bunch of hard disks than to erase
> *and verify*.

Degaussing is for nine-track tapes that you intend to reuse.  If the
disks contain extremely sensitive data grind them up or melt them.  If
not just erase and be happy (if they're broken scrap them for parts and
materials).

The military puts old drives containing sensitive data through a grinder
mostly because two people have to sign a document certifying that they
saw the data destroyed.  You can't see bits being overwritten.
-- 
John Hasler 
jhasler@newsguy.com
Elmwood, WI USA

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#194410

On Monday, April 02, 2018 09:40:40 AM Turritopsis Dohrnii Teo En Ming wrote:
> The foremost question which I want to ask is, what is the universal
> (world wide) understanding behind degaussing hard drives?

...

> 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.

To answer the question as to what is the universal understanding behind 
degaussing hard drives (i.e., did Edward Snowden give you appropriate 
instructions):

I don't think there is a universal understanding. 

If I didn't know Edward very well, I would question his technical competence, 
and ask what he really meant.  (As, to me, among other things, degaussing a 
hard drive is not a normal operation, and, as somebody else has pointed out, 
will not necessarily do the job (of cleaning all "data" (which would include 
the OS, if present) off the disk--or, not knowing how low-level formatting is 
done on hard drives anymore, if really effective, might destroy the low-level 
formatting, and absent some means to restore it, would render the drive 
totally unusable.)

If I knew Edward better, we might have developed a sort of shorthand 
conversation in which I knew that what he meant was to either (1) clean all 
user data (including the OS) off the hard drive for use, for example with a 
different OS, or (2) (maybe a synonym for nuke)--totally destroy the hard drive 
so no one could ever use it (which, for me would probably include either a 
bullet through the disks, or disassemly down to the disks which would then be 
melted in a hot fire.

I suppose, again based on us developing a shorthand, he could mean to clean off 
only the data leaving the OS, but this would be (to me) the least expected 
meaning, and we would have had to have prior discussions in which I understood 
him to be requesting this.

Again, to me, this is the most unusual interpretation of the term degaussing 
with respect to a hard drive.

Hope this helps!

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