How many overwrites for secure erase?

Discussion in 'Computer Security' started by Arthur T., Feb 23, 2008.

  1. Arthur T.

    Arthur T. Guest

    On another list, someone asked a question which piqued my
    curiosity.

    U.S. DoD requires 7 overwrites. The OP wanted a '*technical*
    justification of "15-times" or any other number. Technical one,
    not "because mama said so".'

    Has anyone actually recovered data that's been overwritten
    even once by random data? Twice?

    We know about the theoretical techniques to get the data. We
    know it would be horrendously expensive. But has anyone
    *actually* done it?

    And, regardless, is there some number of overwrites that
    *will* make the data unrecoverable? The OP was looking for
    something better than pulling a number out of the air (or
    wherever) - a number with some theoretical or experimental
    justification.

    I figured if anyone had the answers (and was allowed to give
    them), it would likely be someone in this group.

    --
    Arthur T. - ar23hur "at" intergate "dot" com
    Looking for a z/OS (IBM mainframe) systems programmer position
     
    Arthur T., Feb 23, 2008
    #1
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  2. Arthur T.

    Sebastian G. Guest

    Arthur T. wrote:


    > And, regardless, is there some number of overwrites that
    > *will* make the data unrecoverable?



    Current harddrives are within about 5 to 10 % of the Shannon limit, thus one
    overwrite should suffice.
     
    Sebastian G., Feb 23, 2008
    #2
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  3. From: "Arthur T." <>

    | On another list, someone asked a question which piqued my
    | curiosity.
    |
    | U.S. DoD requires 7 overwrites. The OP wanted a '*technical*
    | justification of "15-times" or any other number. Technical one,
    | not "because mama said so".'
    |
    | Has anyone actually recovered data that's been overwritten
    | even once by random data? Twice?
    |
    | We know about the theoretical techniques to get the data. We
    | know it would be horrendously expensive. But has anyone
    | *actually* done it?
    |
    | And, regardless, is there some number of overwrites that
    | *will* make the data unrecoverable? The OP was looking for
    | something better than pulling a number out of the air (or
    | wherever) - a number with some theoretical or experimental
    | justification.
    |
    | I figured if anyone had the answers (and was allowed to give
    | them), it would likely be someone in this group.
    |

    The DoD requirements are...

    Write a bit pattern such as; 10101010
    Write its complement; 01010101
    Write another pattern such as; 11110000

    Perform that six times.

    The disk will then be sanitized.

    --
    Dave
    http://www.claymania.com/removal-trojan-adware.html
    Multi-AV - http://www.pctipp.ch/downloads/dl/35905.asp
     
    David H. Lipman, Feb 23, 2008
    #3
  4. Arthur T.

    Unruh Guest

    Arthur T. <> writes:

    > On another list, someone asked a question which piqued my
    >curiosity.


    > U.S. DoD requires 7 overwrites. The OP wanted a '*technical*
    >justification of "15-times" or any other number. Technical one,
    >not "because mama said so".'


    > Has anyone actually recovered data that's been overwritten
    >even once by random data? Twice?


    The claim is that in the past, hard drives would tend to keep traces of the
    data. But now, because the manufacturer's are trying to squeeze the last
    ounce of data out of drives, any such residual memory would be a source of
    extra storage, so that modern disks have essentially zero redundancy and
    those old techniques do not work. Ie, overwriting once is enough.

    Note if the data is really that sensitive, overwrite and then destroy the
    disk by a really hot fire


    > We know about the theoretical techniques to get the data. We
    >know it would be horrendously expensive. But has anyone
    >*actually* done it?


    The current claim is that it is not actually doable on modern disks.


    > And, regardless, is there some number of overwrites that
    >*will* make the data unrecoverable? The OP was looking for
    >something better than pulling a number out of the air (or
    >wherever) - a number with some theoretical or experimental
    >justification.


    Destroy the disk by fire. Really hot fire.
    If the data is that secret, the cost of a disk is trivial.


    > I figured if anyone had the answers (and was allowed to give
    >them), it would likely be someone in this group.
     
    Unruh, Feb 23, 2008
    #4
  5. Arthur T.

    Unruh Guest

    "David H. Lipman" <DLipman~nospam~@Verizon.Net> writes:

    >From: "Arthur T." <>


    >| On another list, someone asked a question which piqued my
    >| curiosity.
    >|
    >| U.S. DoD requires 7 overwrites. The OP wanted a '*technical*
    >| justification of "15-times" or any other number. Technical one,
    >| not "because mama said so".'
    >|
    >| Has anyone actually recovered data that's been overwritten
    >| even once by random data? Twice?
    >|
    >| We know about the theoretical techniques to get the data. We
    >| know it would be horrendously expensive. But has anyone
    >| *actually* done it?
    >|
    >| And, regardless, is there some number of overwrites that
    >| *will* make the data unrecoverable? The OP was looking for
    >| something better than pulling a number out of the air (or
    >| wherever) - a number with some theoretical or experimental
    >| justification.
    >|
    >| I figured if anyone had the answers (and was allowed to give
    >| them), it would likely be someone in this group.
    >|


    >The DoD requirements are...


    >Write a bit pattern such as; 10101010
    >Write its complement; 01010101
    >Write another pattern such as; 11110000


    >Perform that six times.


    >The disk will then be sanitized.


    The dod is a bureacracy. Although the recmmendation probably made sense
    once, once they had been promulgated they will never again change no matter
    how the technology changes. To relax them puts someone's ass on the line.
    What if he aralaxes them and suddenly some data leaks. Thus they are frozen
    in time even if they make no sense whatsoever.
    I would not take their recommendation as indicating anything whtsoever
    about what the current best proctice is. While doing what they say may not
    harm except that the wipe taks 2 days rather than 20min.-- which means
    noone does it.

    >--
    >Dave
    >http://www.claymania.com/removal-trojan-adware.html
    >Multi-AV - http://www.pctipp.ch/downloads/dl/35905.asp
     
    Unruh, Feb 23, 2008
    #5
  6. Arthur T.

    Sebastian G. Guest

    Unruh wrote:


    > The claim is that in the past, hard drives would tend to keep traces of the
    > data. But now, because the manufacturer's are trying to squeeze the last
    > ounce of data out of drives, any such residual memory would be a source of
    > extra storage,



    This is a bogus argument. Knowing that you could increase the data density
    doesn't make it any more feasible if its computationally and technically
    expensive.

    > so that modern disks have essentially zero redundancy and
    > those old techniques do not work. Ie, overwriting once is enough.



    Well, at least the corollary holds.

    With increased read speeds, the signals got so badly deluded that they're
    essentially pure sinus waves. Matching with triggers became impossible, so
    currently its done by comparing the signal against a large list (256 or
    more) of signals in parallel and integrating over the absolute difference,
    just to get the best match.
    Since such a technique doesn't allow for any specialized signal codes, they
    were free to resort to the very expensive, generic Turbo(-like) codes. And
    since they had to use these anyway, they could also use their generism and
    efficiency to increase data density to close to the Shannon limit.


    > Note if the data is really that sensitive, overwrite and then destroy the
    > disk by a really hot fire



    Nonsense. The burnt material could shield small pieces of the disc from the
    heat for a very long time.

    Either you have a really really long fire (hours till days) of constant high
    heat, or you may simply resort to degaussing or acid.

    > The current claim is that it is not actually doable on modern disks.



    It is, just the results are not significantly better than educated guessing.
     
    Sebastian G., Feb 23, 2008
    #6
  7. From: "Unruh" <>


    |
    | The dod is a bureacracy. Although the recmmendation probably made sense
    | once, once they had been promulgated they will never again change no matter
    | how the technology changes. To relax them puts someone's ass on the line.
    | What if he aralaxes them and suddenly some data leaks. Thus they are frozen
    | in time even if they make no sense whatsoever.
    | I would not take their recommendation as indicating anything whtsoever
    | about what the current best proctice is. While doing what they say may not
    | harm except that the wipe taks 2 days rather than 20min.-- which means
    | noone does it.
    |

    The standard has changed. What I posted was the NEW standard.

    Don't say "..noone does it.". I see disk sanitization done all the time.

    This isn't something for just Defense organizations. Sanitization should be done by *any*
    company that has company proprietary information stored on their respective hard disks.

    --
    Dave
    http://www.claymania.com/removal-trojan-adware.html
    Multi-AV - http://www.pctipp.ch/downloads/dl/35905.asp
     
    David H. Lipman, Feb 23, 2008
    #7
  8. Arthur T. <> writes:
    > On another list, someone asked a question which piqued my
    > curiosity.
    >
    > U.S. DoD requires 7 overwrites. The OP wanted a '*technical*
    > justification of "15-times" or any other number. Technical one,
    > not "because mama said so".'


    post in another thread
    http://www.garlic.com/~lynn/2008c.html#47 Data Erasure Products
    http://www.garlic.com/~lynn/2008c.html#48 Data Erasure Products

    the above hast reference to NIST standard for overwriting and GAO
    finding that it was adequate ... and then some vendor study finding out
    that they could still recover data (at least in the case of used
    magnetic tape that the gov. was selling ... after overwrites).

    as to disk, some really old email about disk track spacing being reduced
    from 20widths to 10widths (doubling number of tracks ... later to
    2widths).
    http://www.garlic.com/~lynn/2006s.html#email871122
    in this post
    http://www.garlic.com/~lynn/2006s.html#30 Why magnetic drums was/are worse than disks ?

    above also references early work on vertical/perpendicular recording
    .... which more recently is showing up in commodity products
    http://www.garlic.com/~lynn/2007o.html#64 Toshiba Boosts Hard Drive Density by 50%

    this old email doing a different kind of head design (working with the
    person that originated risc chip architecture)
    http://www.garlic.com/~lynn/2006s.html#email871230

    part of the issue use to be small head jitter ... head write surface
    would be wider than head read surface ... to reasonable assure that most
    recent write path would cover the area that subsequent reading head
    would travel. by implication a subsequent write operation might not
    exactly overlap a previous write operation (residual signal from
    previous writes offset to one side or another).

    quicky search engine turns up reference to current issues with
    signal noise from closenest of adjacent tracks

    this reference could imply possibly looking at noise from previous
    writes:
    http://www.lecroy.com/tm/solutions/datastorage/DDNA/default.asp
     
    Anne & Lynn Wheeler, Feb 23, 2008
    #8
  9. Arthur T.

    bealoid Guest

    Arthur T. <> wrote in
    news::

    > On another list, someone asked a question which piqued my
    > curiosity.
    >
    > U.S. DoD requires 7 overwrites. The OP wanted a '*technical*
    > justification of "15-times" or any other number. Technical one,
    > not "because mama said so".'
    >
    > Has anyone actually recovered data that's been overwritten
    > even once by random data? Twice?


    In ye olde days you had "blobby bits" and wobbly heads. You don't have
    that anymore.

    There isn't, AFAIK, anyone offering to recover data from a disc that's
    been over-written even once with all 0's. (Which would be eaiser than
    recovering from an over write of pseudo random data.)

    >a number with some theoretical or experimental
    > justification.


    Here are two theories:

    1) The theory is that you don't know what tech your attacker has, and you
    don't know what tech your attacker will invent in the future, and so you
    over-write many times with patterns and random data, then take the
    platters out and physically destroy them.

    2) You have sensitive information (patient medical stuff, for example)
    and it's just easier to do the belt-and-braces destroy thing than a
    sensible destroy, if only to keep the wing-nuts out of your hair. You've
    removed any doubt.

    People might prefer to do cost-benefit risk analyses - it takes time (and
    thus money) to overwrite disks.
     
    bealoid, Feb 23, 2008
    #9
  10. Arthur T.

    nemo_outis Guest

    "David H. Lipman" <DLipman~nospam~@Verizon.Net> wrote in
    news:9YWvj.397$xg6.104@trnddc07:

    > From: "Unruh" <>
    >
    >
    >|
    >| The dod is a bureacracy. Although the recmmendation probably made
    >| sense once, once they had been promulgated they will never again
    >| change no matter how the technology changes. To relax them puts
    >| someone's ass on the line. What if he aralaxes them and suddenly some
    >| data leaks. Thus they are frozen in time even if they make no sense
    >| whatsoever. I would not take their recommendation as indicating
    >| anything whtsoever about what the current best proctice is. While
    >| doing what they say may not harm except that the wipe taks 2 days
    >| rather than 20min.-- which means noone does it.
    >|
    >
    > The standard has changed. What I posted was the NEW standard.
    >
    > Don't say "..noone does it.". I see disk sanitization done all the
    > time.
    >
    > This isn't something for just Defense organizations. Sanitization
    > should be done by *any* company that has company proprietary
    > information stored on their respective hard disks.



    Sanitizing may be acceptable (I hae me douts) for a drive that is moving
    within an organization (but even then only from and to low security
    uses/users). For any HD leaving the company, the HD should be
    *destroyed.* Many companies that do paper shredding also have a division
    that will mangle HDs (and CDs, etc.) into tiny bits - often with a logged
    secure custody chain, witnessing, etc.

    Wiping is slow (especially for modern very big drives), and there are
    many risks that it will be overlooked or will be done incompletely (e.g.,
    all too easy for one in the "to be wiped" pile accidentally being moved
    to the "wiped" pile without having been wiped).

    HDs are cheap, liabilities are large - too cheap and too large to take
    risks with for data leaking outside the company. Destroy 'em!

    Regards,
     
    nemo_outis, Feb 23, 2008
    #10
  11. Arthur T.

    bealoid Guest

    "David H. Lipman" <DLipman~nospam~@Verizon.Net> wrote in
    news:9YWvj.397$xg6.104@trnddc07:

    [snip]

    > Don't say "..noone does it.". I see disk sanitization done all the
    > time.


    I see lots of people who don't really know what they're doing, and don't
    have particularly sensitive info, "over sanitizing" their disks.

    > This isn't something for just Defense organizations. Sanitization
    > should be done by *any* company that has company proprietary
    > information stored on their respective hard disks.


    I'd hope everyone agrees on that bit! What's up for debate is how much
    overwriting is actually needed.
     
    bealoid, Feb 23, 2008
    #11
  12. Arthur T.

    bealoid Guest

    "Sebastian G." <> wrote in
    news::

    [snip]

    > Either you have a really really long fire (hours till days) of
    > constant high heat, or you may simply resort to degaussing or acid.


    Obviously: Degaussing the platters, not the whole drive. Which I've seen
    people recommend as a way of disk erasing.
     
    bealoid, Feb 23, 2008
    #12
  13. Arthur T.

    Arthur T. Guest

    In Message-ID:<gAUvj.51673$C61.25538@edtnps89>,
    Unruh <> wrote:

    >modern disks have essentially zero redundancy and
    >those old techniques do not work. Ie, overwriting once is enough.
    >
    >Note if the data is really that sensitive, overwrite and then destroy the
    >disk by a really hot fire


    Paraphrased: It's impossible to retrieve the data if it's
    overwritten even once, but if you don't want people to be able to
    retrieve the data, destroy the disk.

    Actually, this is the kind of advice the OP was already
    getting. His question, though, (again, paraphrased) is whether
    there are technical reasons published to show that two wipes are
    (or are not) better than one. And, if one wipe isn't enough, are
    there technical reasons to show that N is enough (for some N).

    I have seen published two methods of attack:

    1. Incomplete magnetization. This is a possible reason to
    require multiple passes with specific kinds of bit patterns. But,
    is there really enough residual data to be read after a wipe with
    a pattern and its complement?

    2. Incomplete coverage. This is the reason for multiple passes
    regardless of the bit patterns. However, by its nature, there's a
    statistical chance that an area written by the real data will be
    missed by every subsequent pass (especially if the disk was jarred
    after writing the real data). This, of course, ignores the
    likelihood that a well-used disk will already have most sectors
    written to several times, so the "real" data is already obscured
    by older data (which is obscured by the "real" data).

    An anti-paranoia note (therefore, possibly not appropriate
    for this newsgroup) on a related topic: A few years back they
    made another attempt to read the 18-minute gap in the Nixon tape
    using the latest and greatest technology. They failed.

    --
    Arthur T. - ar23hur "at" intergate "dot" com
    Looking for a z/OS (IBM mainframe) systems programmer position
     
    Arthur T., Feb 23, 2008
    #13
  14. Arthur T.

    Arthur T. Guest

    In Message-ID:<Xns9A4DA577A884FYAsfKJXSTO@194.117.143.37>,
    bealoid <> wrote:

    >1) The theory is that you don't know what tech your attacker has, and you
    >don't know what tech your attacker will invent in the future, and so you
    >over-write many times with patterns and random data, then take the
    >platters out and physically destroy them.


    Pointing out the possibilities of future tech (and the
    near-impossibility of ruling out what future tech might be) puts
    overwriting into a different perspective. Thank you.

    >2) You have sensitive information (patient medical stuff, for example)
    >and it's just easier to do the belt-and-braces destroy thing than a
    >sensible destroy, if only to keep the wing-nuts out of your hair. You've
    >removed any doubt.


    CYA is a very good reason, but not a technical one ;-).

    >People might prefer to do cost-benefit risk analyses - it takes time (and
    >thus money) to overwrite disks.


    And, it takes even more time and money to do the analysis of
    how much overwriting is necessary. Thus, we're likelier to get
    "guidelines" than reasoned, technical answers.

    So, even if today N overwrites makes a disk unreadable,
    tomorrow someone might find a way to read it. (And, of course,
    even N overwrites might be readable by a closed-mouthed government
    agency.)

    Short of a theoretical proof (which unlikely to have much to
    do with real-world technology), N can be argued but might never be
    enough for absolute security.

    I think this explains the lack of reasons for the guidelines
    currently available.

    Thanks to all who responded to this thread. I responded to
    this post because that's when the answers sunk in, but all of the
    responses were helpful in bringing me to the state where I could
    understand the gestalt.

    --
    Arthur T. - ar23hur "at" intergate "dot" com
    Looking for a z/OS (IBM mainframe) systems programmer position
     
    Arthur T., Feb 23, 2008
    #14
  15. Arthur T.

    Moe Trin Guest

    On Sat, 23 Feb 2008, in the Usenet newsgroup alt.computer.security, in article
    <MNWvj.36872$FO1.1883@edtnps82>, Unruh wrote:

    >"David H. Lipman" <DLipman~nospam~@Verizon.Net> writes:


    >>The DoD requirements are...

    >
    >>Write a bit pattern such as; 10101010
    >>Write its complement; 01010101
    >>Write another pattern such as; 11110000
    >>Perform that six times.

    >
    >>The disk will then be sanitized.


    >The dod is a bureacracy. Although the recmmendation probably made sense


    Obviously, you are not a DOD contractor. The wiping process is NOT a
    recommendation, it is an absolute REQUIREMENT. They tell you to do it,
    and you do - no quibbling, no bullshit.

    >once, once they had been promulgated they will never again change no
    >matter how the technology changes. To relax them puts someone's ass on
    >the line.


    Fine - YOU negotiate the contract to do otherwise. Otherwise, you are
    in violation of the contract, and bad things will happen.

    >What if he aralaxes them and suddenly some data leaks. Thus they are
    >frozen in time even if they make no sense whatsoever.


    Please stop imagining things. Read the requirements - they're public
    knowledge, and note FURTHER that these are not the most stringent of
    data destruction.

    >I would not take their recommendation as indicating anything whtsoever
    >about what the current best proctice is. While doing what they say may
    >not harm except that the wipe taks 2 days rather than 20min.


    So what? Their REQUIREMENT is a REQUIREMENT, not a recommendation, not
    a suggestion. You do it WITH WITNESSES or YOU suffer the consequences.
    Or, do you feel that contract law doesn't apply to you?

    >which means noone does it.


    BULL SHIT! Free clue:

    Web Results 1 - 10 of about 26,300 for computer+data destruction
    Vancouver+BC. (0.21 seconds)

    and that's just Vancouver, BC. The yellow pages here in Phoenix list
    nine companies who will do data destruction and claim to have various
    certifications to do so. We use two of them.

    Old guy
     
    Moe Trin, Feb 23, 2008
    #15
  16. David H. Lipman, Feb 23, 2008
    #16
  17. Arthur T.

    Moe Trin Guest

    On Sat, 23 Feb 2008, in the Usenet newsgroup alt.computer.security, in article
    <>, Arthur T. wrote:

    >bealoid <> wrote:


    >>People might prefer to do cost-benefit risk analyses - it takes time
    >>(and thus money) to overwrite disks.

    >
    > And, it takes even more time and money to do the analysis of
    >how much overwriting is necessary. Thus, we're likelier to get
    >"guidelines" than reasoned, technical answers.


    If you are not a DOD contractor, then you have to make a reasoned
    guess of what you are trying to protect against. (If you are a
    DOD contractor, then you just do _exactly_ what the contract says
    you are to do - no more, no less.) Are you worried about your
    competitor finding a used hard drive that has the secret ingredients
    of your Whizzo Cola(tm)? Are you worried about the cops finding a
    list of your customers for that fantastic Reindeer Dust? Or it this
    the theory of how to make gasoline from sea water at a cost of $0.51
    a barrel, using a solar powered boiler made from used tin-cans?

    > So, even if today N overwrites makes a disk unreadable,
    >tomorrow someone might find a way to read it. (And, of course,
    >even N overwrites might be readable by a closed-mouthed government
    >agency.)


    Ah, but recall that N overwrites is only acceptable up to certain
    specified classification levels. If it's "The Deep Dark Secret That
    No One Should Ever Know About", the correct answer is to slag the
    drive - physical destruction of the media, followed by melting the
    residue. It's kind of hard to get anything off a ceramic platter
    when the platter is now a new glass coffee mug, and the aluminum
    platter is now a new can of Belch Beer. If that's what happened to
    the media, think what remains of the magnetic patterns on the (also)
    melted residue. Is that a one, or a zero transition here, and
    where does that fit into which file?

    > Short of a theoretical proof (which unlikely to have much to
    >do with real-world technology), N can be argued but might never be
    >enough for absolute security.


    Bingo!

    > I think this explains the lack of reasons for the guidelines
    >currently available.


    There are guidelines. What you have to determine is if any of them
    apply to you or your situation.

    Old guy
     
    Moe Trin, Feb 24, 2008
    #17
  18. Arthur T.

    Moe Trin Guest

    On Sat, 23 Feb 2008, in the Usenet newsgroup alt.computer.security, in article
    <YBZvj.234$R_5.180@trnddc08>, David H. Lipman wrote:

    >From: "Moe Trin" <>


    >| and that's just Vancouver, BC. The yellow pages here in Phoenix list
    >| nine companies who will do data destruction and claim to have various
    >| certifications to do so. We use two of them.


    >Any DoD Contractor can have the NSA CMC destroy the disks and receive a
    >receipt indicating their destruction. :)


    I'm not exactly sure how our DOD stuff is handled, as it's not my
    bailiwick. On the other hand, I'm guessing that about a quarter of the
    drives here go out for a certified scrub because we're a R&D facility
    and corporate is rather paranoid about some things. Heck, all of the
    waste paper trash is shredded, even if it came from the chief cook's
    office in the employee's cafeteria, just as all hard drives get a 3
    pass (zeros, ones, "random data") wipe when they are taken out of
    service. Something like 15 minutes per Gig - big deal, especially
    when you have several "dedicated" boxes to do the job.

    Old guy
     
    Moe Trin, Feb 24, 2008
    #18
  19. Arthur T.

    nemo_outis Guest

    (Moe Trin) wrote in
    news::

    ....
    > Ah, but recall that N overwrites is only acceptable up to certain
    > specified classification levels. If it's "The Deep Dark Secret That
    > No One Should Ever Know About", the correct answer is to slag the
    > drive - physical destruction of the media, followed by melting the
    > residue. It's kind of hard to get anything off a ceramic platter
    > when the platter is now a new glass coffee mug, and the aluminum
    > platter is now a new can of Belch Beer.



    Roasting is messy, hard on the environment, and can be unsafe, although
    getting the disks and heads hotter than the Curie/Neel temperature is
    effective and reasonably doable by amateurs.

    The preferred method for complete destruction is degaussing by a machine
    designed for the purpose (preferably over 8000 Gauss - machines are
    available as high as 13000 Gauss) followed by shredding. Such degaussers
    work quickly through the drive casing, warp heads, etc, and remove all
    magnetic info from the drive including servo tracks, etc. This alone
    irretrievably blitzes the drive. Shredding puts the final nails in the
    coffin.

    Cost for degaussing and shredding (with custody and audit trail) is about
    $10-15/drive in reasonable quantities - probably considerably more on a
    onesy-twosy basis. You can usually even arrange to witness the
    destruction (sometimes for a fee) although some shops will balk about
    safety/liability issues. Best method is to try to piggyback on a company
    that already has a data/drive destruction contract with one of these
    shops (they're often associated with, or part of, a commercial secure
    paper-shredding shop).

    Regards,
    ..
     
    nemo_outis, Feb 24, 2008
    #19
  20. Arthur T.

    Unruh Guest

    bealoid <> writes:

    >"Sebastian G." <> wrote in
    >news::


    >[snip]


    >> Either you have a really really long fire (hours till days) of
    >> constant high heat, or you may simply resort to degaussing or acid.


    >Obviously: Degaussing the platters, not the whole drive. Which I've seen
    >people recommend as a way of disk erasing.


    Degaussing would I think be a terrible technique. It wold leave data all
    over the place. Fire will do it-- raise the temp about the neal point and
    the domains all disappear.
     
    Unruh, Feb 24, 2008
    #20
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