On Tue, Aug 30, 2011 at 12:00 AM, Andrew S. Baker <[email protected]> wrote: > https://www.infosecisland.com/blogview/16130-The-Urban-Legend-of-Multipass-Hard-Disk-Overwrite.html
I have never seen an official copy of NISPOM (DoD 5220.22-M) that specified specific overwrite methods. I seriously wonder if that one copy hanging out on that US Aid site that the entire Internet has found is someone's convenience modification. In any event, NISPOM is a very broad scope document; sanitization is a couple of paragraphs out of ~150 pages. For systems under DSS jurisdiction (most government contractors), DSS provides a separate "Clearing & Sanitization Matrix" (which incidentally looks just like the table in that US Aid NISPOM). It's driven by the NSA, and updated periodically. Since 2007, overwrite of any sort is no longer considered acceptable for magnetic disks containing classified information. Physical destruction or degaussing are the only acceptable methods. The reasons for this are not publicly known. As the author of the article points out, it may be procedural as much as technological -- rather than trying to keep up with recording methods, the NSA may have decided to just go with methods known to work in every case. On the other hand, the NSA absolutely knows things we don't. On the third hand, modern hard drives do all sorts of things behind the scenes. An overwrite may not cover everything. In particular, hard disks can transparently remap blocks, and don't necessarily promise to do anything about the physical block previously holding your sensitive data. I'm somewhat amused that, despite a page full of conflicting previous references, the author of the article considers that one paper to be the final word. All that said, if you're not protecting information relevant to national security, I'd expect overwrite to be sufficient. Maybe run a couple of passes, just to be thorough. -- Ben ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to [email protected] with the body: unsubscribe ntsysadmin
