A much better article on the topic can be found at http://www.cs.auckland.ac.nz/~pgut001/secure_del.html The problem is that data that's been written over once, or even twice or ten times, can often still be read if someone actually takes the platters out and uses electromagnetic microscopy on them. If you "erase" data using the perl script in the article Jim pointed at, it will be safe from J. Random who doesn't have much time, money, or technique to spend on it. But it won't be safe from TLA's, commercial data-recovery shops, or any seriously "hardcore" hackers (or people who, for example, know enough to take it to a commercial data-recovery shop). To actually finish the job, you'd want extremely low-level access to the drive, including the ability to micro-adjust the head alignment so as to write garbage both hubward and rimward of where the track you're trying to erase *ought* to be within its sector, which of course would require you to be able to relocate the info on the sectors physically hubward or rimward of the track you were trying to erase, because writing hubward or rimward with micro-adjustments within a sector could cause errors on those adjacent sectors. I don't know of any OS that provides sufficiently low-level HD access to allow people to create a portable utility that does really secure deletion. Hell, a lot of Hard Drives don't even have drivers that support the needed operations. The moral of the story is, in a really secure system, the plaintext NEVER hits your hard drive. Bear On Mon, 19 Feb 2001, Jim Choate wrote:
http://linuxtoday.com/news_story.php3?ltsn=2001-02-18-016-20-PS-HW-HL -- The Laws of Serendipity:
1. In order to discover anything, you must be looking for something.
2. If you wish to make an improved product, you must first be engaged in making an inferior one.
Tivoli Certification Group, OSCT James Choate jchoate@tivoli.com Senior Engineer 512-436-1062