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From: grady@netcom.com (1016/2EF221)
Subject: Declassifying media
Message-ID:
Organization: capriccioso
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Date: Mon, 5 Apr 1993 21:02:33 GMT
There are many Urban Legends (maybe this ought to be in the Crypt
FAQ?) about what is actually sufficient to clear or declassify
magnetic media when used for classified data. Here is some
information "from the horse's mouth".
(Regarding the sufficient overwriting of media ("clearing") meant to
be *retained* within the controlled environment, or declassifying
the material to be reused *outside* the controlled environment,)
From National Telecommunications and Information Systems
Security (NTISS) "Advisory Memorandum on Office Automation
Security Guidelines" (NTISSAM COMPUSEC/1/87):
------
"7.6.2.1 Clearing of Magnetic Media
Certain types of removable media (e.g., magnetic tape, floppy disk,
cassettes, and magnetic cards) may be cleared by overwriting the
entire media one time with any one character. Floppy disks may be
cleared by applying a vendor's formatting program that overwrites
each location with a given character.
Fixed media (e.g., Winchester disks) should be cleared by overwriting
at least one time with any one character. One way to do this is by
applying a vendor-supplied formatting program that overwrites each
location on the disk with a given character, if it can be shown that
this program actually works as advertised. The user should beware:
some programs that purport to overwrite all locations do not
actually do this.
Cleared media may be resides within the controlled facility or
released for destruction; however, they should be marked and
controlled at the level of the most restrictive sensitivity of
information ever recorded.
7.6.2.2 Declassification of Magnetic Media
Certain types of removable media can be declassified using a
degaussing device that has been approved for declassifying media of
that type. (A list of approved devices is maintained by the NSA.)
If a fixed medium (for example, a hard, or Winchester, disk) is
operative, an approved method of declassifying the disk pack is to
employ an overwrite procedure which must overwrite all
addressable locations at least three times by writing any character,
then its complement (e.g., binary ones and binary zeros)
alternatively.
When fixed media become inoperative, it is impossible to declassify
the media by the overwrite method. In this case, there are two
alternate procedures that may be used: (1) disassemble the disk
pack, and degauss each platter with the appropriate approved
degaussing equipment; and (2) courier the inoperative media to the
vendor's facility, have the magnetic media (e.g., disk platter)
removed in sight of the courier and returned to the courier for
destruction at the secure site. The vendor can then install new
platters and repair any other problems with the disk unit.
7.6.3 Destruction of Magnetic Media"
[see DoD Computer Security Center, "Department of Defense Magnetic
Remanence Security Guideline", CSC-STD-003-85 FOR OFFICIAL USE
ONLY]
------
This and many other interesting documents (many that are more
informative than probably intended) on computer security procedures
can be obtained (free) from:
Executive Secretary
National Telecommunications and Informations
Systems Security Committee
National Security Agency
Fort George G. Meade, MD 20755-6000
Write them! It's fun to be on the NSA's mailing list...
--
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