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What was considered the best practice, or "military-grade" procedure, for protecting secrets stored on floppy disks when disposing of the old disks?

  • 4
    Scissors? Seriously, securely erasing floppies would be a waste of time, since they're not expensive and are easily destroyed. – another-dave Apr 29 at 22:03
  • Disposal in a burn bag was one option. – Jon Custer Apr 29 at 22:19
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    Disposing of the disks was a small risk, compared with preventing unauthorized copies being made. There was no need to burn disks - just put the magnetic material through an office shredder. – alephzero Apr 29 at 23:11
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    There may have been different procedures depending on how quickly it needs to be done and whether it's important for the building to remain standing! – snips-n-snails Apr 29 at 23:21
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    @Raffzahn It would be on topic at Information Security. We have lots of questions like that there. But the existing and accepted answer is absolutely correct. Physical destruction or degaussing is the most effective way to destroy a floppy. – forest May 1 at 3:32
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This document from the NSA, NSA/CSS Storage Sanitization Manual: Purpose and Scope, even though from 2014, is a good summary of how governments have been doing secure destruction of media for a long time: note that all the methods are very old-school! Other government agencies, both in the US and internationally, likely use very similar methods. As far as I can tell, the major changes have been in adding new types of media in the recommendations (and altering the list of manufacturers and devices.)

Regarding diskettes in particular, the procedures are detailed on page 5:

[3. Magnetic Disks: Magnetic disks include hard disk drives and diskettes.] [...]

b. Diskettes

1) Sanitization: Sanitize diskettes by using one of the following procedures. Remove all labels or markings that indicate previous use or classification.

a) Degaussing: Degauss the diskettes in an NSA/CSS evaluated degausser; see Reference b.

b) Disintegration: Disintegrate diskettes using an NSA/CSS evaluated disintegrator; see Reference d.

c) Incineration: Material must be reduced to ash.

d) Shredding: Shred diskettes using an NSA/CSS evaluated crosscut shredder; see Reference e. Remove diskette cover and metal hub prior to shredding.

[...]

So you can take your pick of degaussing the disk, shredding it in a paper shredder, disintegrating it (apparently thinner but longer shreds), or burning it. If you're really interested in what devices the NSA approves, they are listed here.

  • I like the warning to remove the metal parts before shredding. – JeremyP Apr 30 at 9:19
  • I am surprised that they would suggest degaussing, unless that word refers to a very specific procedure, done with a specific, medium-appropriate tool. Even if your computer can no longer read the disk after you've waved a "degaussing coil" over it, that does not prove that you've achieved anything near a "must be reduced to ash" level of erasure. – Solomon Slow Apr 30 at 13:07
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    @SolomonSlow as you can see behind the link, they have a list of approved degaussers, which, if operated in the manufacturer-recommended manner, will wipe data to the NSA's satisfaction. A coil of wire from the junk drawer, wound around a plywood frame and hooked to the mains isn't on the list :) – hobbs Apr 30 at 20:15
  • I remember some of the degaussers used to destroy some hard drives in the military. Some of those drives seemed like they almost exploded. And when we had to destroy our old classified 9 track tapes, we had to cut them into strips and wrap in newspaper before shredding, otherwise the tapes could melt and stick inside the industrial shredder. – riffraff169 May 5 at 18:37

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