Amazon.com just posted my five star review of Forensic Discovery. I read a pre-publication draft of the book which resulted in my quote on the Addison-Wesley site. From the review:
"Farmer and Venema do for digital archaeology what Indiana Jones did for historical archaeology. 'Forensic Discovery' unearths hidden treasures in enlightening and entertaining ways, showing how a time-centric approach to computer forensics reveals even the cleverest intruder. I highly recommend reading this book."
In the chapter 7 (available online as a .pdf) Farmer and Venema mention the Veeco Nanotheater. Veeco makes products which can scan the surface of disks at nanotechnology scales. They show the image at right, and describe it as "residuals of overwritten information on the sides of magnetic disk tracks." This demonstrates the difficulty of truly "destroying" digital evidence. Forensic Discovery explains the problem this way:
"Although memory chips and magnetic disks are designed to store digital information, the underlying technology is analog. With analog storage of digital information, the value of a bit is a complex combination of past stored values. Memory chips have undocumented diagnostic modes that allow access to values smaller than a bit. With modified electronic circuitry, signals from disk read heads can reveal older data as modulations on the analog signal."
At 198 pages this book is a quick read, which explains how I was able to read and review it while writing a new book!