Messages in this thread | | | Date | Tue, 22 Dec 1998 16:57:24 -0500 | From | "Theodore Y. Ts'o" <> | Subject | Re: Wanted: Secure-delete utility for Linux |
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There's a very good paper on the subject given at a Usenix Security Symposium, I think 2 years ago. It showed exactly how much information you could glean off of a magnetic disk platter using an electron microscope to read out the old magnetic domains. It was absolutely spooky --- he was able to read data that had been written several write generations beforehand. That's why secure deletion programs will do 20-30 write passes, and I believe that for highly classified data, even that's not good enough. (Sandblasting the magnetic media off the platters --- when you care enough to destroy the very best. :-)
So it's not just super-spooky three-letter agencies that can pull off this sort of thing. It's something doable for folks with access to openly available technology (at least to those of us who hang around universities or other research facilities).
- Ted
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