From: Bill Stewart <stewarts@ix.netcom.com>
Date: Thu, 3 Jul 1997 08:18:23 +0800
To: 3umoelle@informatik.uni-hamburg.de (Ulf Möller)
Subject: Re: Degaussing
In-Reply-To: <19970702021749.17094.qmail@squirrel.owl.de>
Message-ID: <3.0.2.32.19970702160205.0310cb98@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



>> Could someone please point me to a FAQ or somesuch about degaussing
>> magnetic media? Thank you!
> http://www.cs.auckland.ac.nz/~pgut001/secure_del.html 

Thanks for posting a marvelous reference on erasing media.
Technology changes have a substantial effect on what's
adequate and what's not.  Back in the mid-late 80s, 
when I was a tool of the military-industrial complex, 
we had the offical rules for declassifying media;
I think they were from Army Reg 380-380.

For disk drives and magtapes, you had the choice of
physical destruction, running an NSA-approved overwrite program,
or using an NSA-approved BF magnet for degaussing.
We didn't have an approved program for Vax UNIX,
not that I would have trusted it to clean mapped-out bad sectors,
and any magnet that could suck the bits off a hard disk
was bigger than I was going to allow near my computers
or mag tape collection, thank you very much.

Floppy disks make a satisfying squooshy sound in a shredder;
remember to take the cardboard jacket off the floppy first.
Reeling out 9-track tape into a shredder is boring, but works.
I was no longer around when they sandblasted the RM05 packs,
but the sysadmin after me had a good time doing it,
and instead of the usual head-crashed RM05 platter on her wall,
she had one that was sandblasted real clean :-)

For memory, you needed to run an NSA-approved program
on your machine that would overwrite each byte three (?) times;
the trick was making sure your operating system would let you
get at everything, and of course moving the program while it
was running so it wouldn't overwrite itself.
I don't know if anyone remembered to do that after decommissioning
the VAX; we didn't do it when switching between the classified 
operating system diskpacks and the VMS maintenance system,
but we still maintained physical control of the system so it was OK.

Technology changes make a lot of difference in how you operate;
When we were using Vaxen with large RM05 removable disks,
we'd keep the main copy of the operating system up and running,
and needed to pay a lot of attention to security (in spite of most
of our users having the root password :-), and the disk packs
took up lots of space in the safe.  Later we started using PCs,
and any special project that didn't want to run on the main Vax
just kept a few floppies in the safe, or if it had a hard disk,
they could put the whole PC in the safe.  With Sun workstations,
we switched over to using shoebox disks, which were very convenient...
Now if I were in that business, I suppose I'd use Jazz drives,
or the large Syquest drives, and keep the operating system
on a read only hard drive...


#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk/pub/crypto/pgp
#   (If this is a mailing list or news, please Cc: me on replies.  Thanks.)