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Newsgroups: sci.crypt Path: cantaloupe.srv.cs.cmu.edu!crabapple.srv.cs.cmu.edu!fs7.ece.cmu.edu!europa.eng.gtefsd.com!emory!swrinde!sdd.hp.com!decwrl!netcomsv!netcom.com!grady From: grady@netcom.com (1016/2EF221) Subject: Declassifying media Message-ID: Organization: capriccioso X-Newsreader: TIN [version 1.1 PL6] 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... -- grady@netcom.com 2EF221 / 15 E2 AD D3 D1 C6 F3 FC 58 AC F7 3D 4F 01 1E 2F
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