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

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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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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

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