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From: Glenn_Everhart at bankone.com (Glenn_Everhart@...kone.com) Subject: Erasing a hard disk easily Seems to me I recall there are some generic scsi commands to read (try to read) or try to reformat bad sectors. However the point below is still correct: the vendor might not have implemented them correctly, if at all. If they work that just means some things can be done that affect bad blocks without having to have vendor specific command manuals. -----Original Message----- From: full-disclosure-admin@...ts.netsys.com [mailto:full-disclosure-admin@...ts.netsys.com]On Behalf Of Gary E. Miller Sent: Wednesday, July 14, 2004 2:08 PM To: Darren Reed Cc: full-disclosure@...ts.netsys.com Subject: Re: [Full-Disclosure] Erasing a hard disk easily ********************************************************************** This transmission may contain information that is privileged, confidential and/or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is STRICTLY PROHIBITED. If you received this transmission in error, please immediately contact the sender and destroy the material in its entirety, whether in electronic or hard copy format. Thank you ********************************************************************** -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Yo Darren! On Wed, 14 Jul 2004, Darren Reed wrote: > Too bad the pc Unixes don't have a format command like Sun has had > for Solaris/SunOS....tells the hard drive to 'format' and then tests > with a number of test patterns. You can not really force a low level format of an IDE or SCSI drive. The drive that appears to the OS is not the real drive, but a virtual drive managed by the disk electronics. The most you can do is ask the drive to format itself. Some do a good job and some do not. The ones that return in seconds did not and the ones that takes hours are doing better. One thing that has been missed in these discussions are the "spare sectors" present on all IDE and SCSI disks. I am not talking about the "bad blocks" stored in FAT tables and such, but hidden sectors managed by the drive itself. Each drive vendor has vendor specific commands for accessing and managing theese spare sectors and bad sectors. There is no generic method. Some consider this proprietary info and some readily release it. If the drive notices soft errors in a given sector it will copy the data to a "spare sector", then move the bad sector to a bad sector list and use the formerly spare sector in it's place. The OS never noticed that anything happened. The old data remains in the bad sector and can be recovered. You can format the drive as it appears to the OS as much as you want, but unless you get "low level" with the drive you are NOT touching the spare and bad sectors. They may very well contain data you do not want to be read. If you give me one of these drives, I might be able to get vendor data on how to read the bad sectors and then I would have your data! This is not as long a shot as it would seem. Just before your drive dies it may be doing a lot of thrashing of bad/spare sectors in a last attempt at staying alive. Often used files like /etc/passwd and gpgkeys are more likely to be accessed and therefore more likely to have a copy in the bad sector table. You throw the drive away and I get it from the dumpster. Often I can put dead HS in the refrigerator and get it to work for a few more hours longer than you could. RGDS GARY - --------------------------------------------------------------------------- Gary E. Miller Rellim 20340 Empire Blvd, Suite E-3, Bend, OR 97701 gem@...lim.com Tel:+1(541)382-8588 Fax: +1(541)382-8676 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (GNU/Linux) iD8DBQFA9XaP8KZibdeR3qURAt+2AKCnRWaro6/mUok1l46Zz2mMNE/cWQCg7Fr0 X14ASFMPd8CikeCxAoYqPu0= =em1t -----END PGP SIGNATURE----- _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html ********************************************************************** This transmission may contain information that is privileged, confidential and/or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is STRICTLY PROHIBITED. If you received this transmission in error, please immediately contact the sender and destroy the material in its entirety, whether in electronic or hard copy format. Thank you **********************************************************************
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