The data only has to be overwritten once such that it is unrecoverable using standard forensic recovery methods. Secondly, the point of overwriting with several passes is to generate enough magnetic force to switch the domains and may or may not work, depending on the physical characteristics of the drive. I suspect that in most cases, it won't as it isn't that easy when dealing with the threat of MFM/STM/*[F|T|I|P]M
You have to have an understanding of the particulars of the scheme used by the drive for encoding data (and its variants) to properly design alternating overwrite patterns that don't repeat, and will work, not to mention an understanding of its physical characteristics as was mentioned by Matthew. more info: http://www.cs.auckland.ac.nz/~pgut001/secure_del.html _________________________________________ John Daniele Technical Security & Intelligence Toronto, ON Voice: (416) 605-2041 E-mail: [EMAIL PROTECTED] Web: http://www.tsintel.com On Sun, 3 Mar 2002, Matthew Tallon wrote: > > Hi, > > > the safe side and use 7 passes to be thorough. If memory > > serves, seven passes is also the DoD standard (along with > > randomized non-sensitive data for the re-write). > > I don't want to beat this one to death, but more than a few > questions bounce around in my head. Any physics majors or hd > gurus out there? Having a fair amount of experience in the > audio field, I understand the issues involved with analog > recordings but I know very little about the details of digital > media. > > This seems to imply that if I re-write the same data to the same > location on a disk, the bits are magnetically stronger with each > write, or even that under normal use, I could extract (under > optimal conditions) several generations of data from the same > location on the disk. I suppose various vendors would create > heads that write stronger signals to disk and would prove more > reliable from a security (and integrity) point of view. > > Sort of going back to college, can someone point me to an > authoritative breakdown of hard drive media? I have to admit, > my curiosity is thoroughly piqued! > > Thanks, > > Matthew Tallon > >
