Date: Sat, 15 Apr 2000 12:51:44 -0600 (MDT) From: Reid Orsten <rorsten@gpu.srv.ualberta.ca> To: Ben Smithurst <ben@scientia.demon.co.uk> Cc: Scott Blachowicz <scott@sabmail.rresearch.com>, freebsd-questions@FreeBSD.ORG Subject: Re: Erasing an IDE disk Message-ID: <Pine.A41.4.10.10004151247240.27074-100000@gpu1.srv.ualberta.ca> In-Reply-To: <20000415165532.A16019@strontium.scientia.demon.co.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sat, 15 Apr 2000, Ben Smithurst wrote: > Scott Blachowicz wrote: > > > I'm fixing to remove a disk from my system and give it to someone else. I want > > to erase it to try to make sure that no personal or sensitive data can be > > recovered from it. So, my first attempt was to install FreeBSD 4.0 on it, then > > try to do this kind of stuff: > > > > dd if=/dev/zero of=/dev/ad0s2c > > That will only erase slice 2, so that's not really good enough. You > won't be able to erase the whole disk unless nothing on ad0 is mounted > (did you check that; what does "mount" show?). I think what you'll have > to do is to put this disk in another FreeBSD system as ad1 (or ad2, or > whatever), and try erasing /dev/ad1 completely (not ad1s<something> > or anything like that). Or, you could use the fixit CD (disc 2 in WC > sets), and use dd from there. > > As for the person who suggested /dev/urandom, I'm not sure > that would be better. It will use loads of CPU time, both > ways will stop a casual nosy person, and neither way will > stop someone who *really* wants the data off the disk. See > <http://www.cs.auckland.ac.nz/~pgut001/secure_del.html>; for more on this > sort of stuff. > > When I returned a disk to a shop recently because it was b0rken, I just > wrote 0x0, 0xff, then 0x0 over the whole disk. Given that when I took > it back they used Windows Scandisk to check if it really was faulty, I > think that was overkill. :-) > > -- > Ben Smithurst / ben@scientia.demon.co.uk / PGP: 0x99392F7D > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message > Bruce Schneier, well respected cryptographer suggests the following method for erasing a disk securely: "I recommend overwriting a deleted file seven times: the first time with all ones, the second time with all zeroes, and five times with a cryptographically secure pseudo-random sequence." If its sensitive data, that's the way to go. Reid To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.A41.4.10.10004151247240.27074-100000>