Security Basics mailing list archives
RE: Interesting One
From: "Trevor Cushen" <Trevor.Cushen () sysnet ie>
Date: Thu, 31 Oct 2002 11:58:58 -0000
Thanks James Taylor I was wondering where I got the seven from. I have looked at the DOD standard that disk wiping products talk about and it has no number in it (Orange book). Other US government documents talk about three levels of disk destruction, wiping, degaussing, and destruction. This may be where the various numbers are coming from. Another post talked about the US government saying 7 also so "it must be secure". I won't go by that since the same US government wants encryption levels kept down so they can break them. Do they want the same from disk wipes??? Yes a bit paranoid conspiracy stuff alright, I agree. I think the concensis seems to be that a good overwrite of all sectors 2-3 times will make the disk pretty much safe for reuse if the data is not highly sensitive. If it is then burn the disk and buy a new one instead of reusing it. Also it seems clear that if it is possible to recover data that was overwritten 30 times it is not something that would have been done easily. It takes great effort, expensive equipment, and expertise. If your repair guy could get data then why was he looking and what did he get. I would agree it was scare mongering for a sale of some disk wiping software package they just happen to sell. Do they sell something like this??? Trevor Cushen Sysnet Ltd www.sysnet.ie Tel: +353 1 2983000 Fax: +353 1 2960499 -----Original Message----- From: James Taylor [mailto:james_n_taylor () yahoo com] Sent: 30 October 2002 04:50 To: security-basics () securityfocus com Subject: Re: Interesting One The CISSP Study Guide (ISBN 0-471-41356-9) states that: "Information on magnetic media is typically 'destroyed' by degaussing or overwriting. Formatting a disk once dones not completly destroy all data, the entire media must be overwritten or formatted seven times to conform to standards for object reuse". Also the above book states that "the Orange Book standard reccommends that magnetic media be formatted seven times before discard or reuse of media". So if the US gov't reccommends seven times, you can bet that they have technology that can read to a lower level than that! However 30 times seems a bit excessive and it must depend on the nature of the data being overwritten and what area's of the media have been completly destroyed. At that level I imagine it's something like guessing the picture from a 10000 piece jigsaw puzzle, with most of the pieces missing. Regards James --- Carol Stone <carol () carolstone com> wrote:
I don't know much about this, but yesterday I read in one of the later chapters of Bruce Schneier's book, "Secrets and Lies," (link to amazon follows) that over-writing data on a disk does *not* completely obliterate it, it just makes it a lot more difficult to recover with each over-write. I believe he said just how many re-writes were still recoverable was a secret one of our governmental organizations wasn't about to give up. I'll look at my book later when I have it in my hands and see if I can't find part and post a pointer to *his* reference. -carol http://www.amazon.com/exec/obidos/tg/detail/-
/0471253111/qid=1035924654/sr=8-3/ref=sr_8_3/104-4454644-5987143?
v=glance&n=507846Greetings Folks, I had an interesting conversation today with someonefrom FAST(Federation Against Software Theft) They pretend not to be a snitchwing of the BSA.Anyway, to get to the point, the guy that came to seeme said that theirforensics guys could read data off a hard drive thathad been writtenover up to thirty times. I find this very hard to believeand told him Ithought he was mistaken but the guy was adamant that it couldbe done. Myquestion is, does anyone have any views on this, or, can anyonepoint me to asource of information where I can get the facts on exactly howmuch data can beretrieved off a hard drive and under what conditionsetc etc.Thanks Dave Adams This message (and any associated files) is intendedonly for theuse of the individual or entity to which it isaddressed and maycontain information that is confidential, subject tocopyright orconstitutes a trade secret. If you are not the intendedrecipientyou are hereby notified that any dissemination, copyingordistribution of this message, or files associated withthis message,is strictly prohibited. If you have received thismessage in error,please notify us immediately by replying to the messageand deletingit from your computer. Messages sent to and from John Crowley (Maidstone) Ltd may be monitored. Internet communications cannot be guaranteed to besecure or error- freeas information could be intercepted, corrupted, lost,destroyed, arrivelate or incomplete, or contain viruses. Therefore, wedo not acceptresponsibility for any errors or omissions that arepresent in thismessage, or any attachment, that have arisen as aresult of e-mailtransmission. If verification is required, pleaserequest a hard-copyversion. Any views or opinions presented are solelythose of the authorand do not necessarily represent those of John Crowley(Maidstone) Ltd.-- Real people for the virtual world. http://www.elirion.net
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Current thread:
- RE: Interesting One lvickers (Oct 31)
- <Possible follow-ups>
- RE: Interesting One Jimmy Liang (Oct 31)
- Re: Interesting One easy (Oct 31)
- RE: Interesting One Michael Vaughan (Oct 31)
- Re: Interesting One Candice Ward (Oct 31)
- RE: Interesting One Tim Donahue (Oct 31)
- RE: Interesting One Carol Stone (Oct 31)
- RE: Interesting One Rygg Christian (Oct 31)
- RE: Interesting One Trevor Cushen (Oct 31)
- Re: Interesting One ONEILL David J (Nov 01)
- Re: Interesting One Greg van der Gaast (Nov 01)
- RE: Interesting One Leonard.Ong (Nov 01)
- RE: Interesting One Holmes, Ben (Nov 01)
- RE: Interesting One Trevor Cushen (Nov 01)
- Re: Interesting One Meritt James (Nov 01)
- Re: Interesting One Chet Uber (Nov 01)
- Re: Interesting One Pablo Gietz (Nov 01)
- RE: Interesting One Rodney, John (Nov 01)