I'm interested in performing an audit of our outsourced data
sanitizing service.  I am part of a medium sized business who just let
go of 17 older computers.  These computers were given to another
company to be cleaned of all data and then sold at an auction.  We
repurchased the 17 computers and now wish to perform data recovery and
forensics on the hard drives.  The drives are a mixed bunch of 1-4
gigs with varying interfaces, most are different types of SCSI and
there are a few ATA.

At first glance, many of the HDs from x86 computers appear to have
Windows 95 on them; their previous data appears to have been
overwritten simply with the format on a Windows disk.  A similar
strategy seems to have been employed on the Apple HDs.  The HDs from
the Sun SPARCs appear to be empty.

So far I've plugged all the drives into a Linux box and made dd
(sometimes dcfldd) images with them.  I'm attempting to analyze the
images with:
EnCase Forensic Edition - http://www.encase.com/products/EnCaseForensic/index.shtm
Ontrack EasyRecovery Professional - http://www.ontrack.com/easyrecoveryprofessional
The Sleuth Kit/Autopsy - http://www.sleuthkit.org/
PyFLAG - http://pyflag.sourceforge.net/

I think it may be possible to get access to more data than I have at
this time through low-level analysis of the hard drives' error
correction capabilities, some like to call this method of analysis
"magnetic resonance".  I think this may be the type of access that
programs like SpinRite (http://grc.com/spinrite.htm) have (apparently,
it is written in straight assembler).  However, SpinRite is unsuitable
for this experiment because it only recovers data from drive failure. 
I would need to modify its operation to look for old data underneath
new data, a type of forensics operation that it is not capable of.

Can anyone tell me of a program that provides this type of low-level
access to these hard drives that would be neccessary for me to recover
more data?  Don't worry if the product is commercial or costs a
fortune.

I may increase the bounty on this question if the answer seems worth it.

---

Clarification of Question by dguido-ga on 29 Jan 2005 23:04 PST

I should clarify, that the answer doesn't neccessarily have to be
about software that does exactly what I specified.  If there is some
type of software I'm missing that you think would help me accomplish
what I'm going for, name it!  The only things you shouldn't include
are high-priced hardware solutions, like building a clean room.  I'll
even accept answers with hardware as long as it's reasonable in price,
say < $500.

---

Clarification of Question by dguido-ga on 03 Feb 2005 12:36 PST

This also may be of use.  Its contents is dated and not as helpful as
I'd like: http://www.usenix.org/publications/library/proceedings/sec96/full_papers/gutmann/