I loved Designing BSD Rootkits (DBR) by Joseph Kong, and I'm not even a kernel hacker. Rather, I'm an incident responder and FreeBSD administrator. This book is directly on target and does not waste the reader's time. If you understand C and want to learn how to manipulate the FreeBSD kernel, Designing BSD Rootkits is for you. Peer into the depths of a powerful operating system and bend it to your will!
DBR covers much of the same sorts of material found in the earlier Rootkits: Subverting the Windows Kernel by Greg Hoglund and James Butler, except Kong's book is all about FreeBSD. I actually read the Windows text first, but found Kong's more direct language and examples easier than the Hoglund/Butler text. After reading DBR I have a stronger understanding of each of the main chapters' techniques, i.e., kernel modules, hooking, direct kernel object manipulation, kernel object hooking, run-time kernel memory patching, and detection mechanisms. I particularly liked the author showing his sample rootkit's effectiveness against Tripwire, simply to demonstrate his methods.
DBR follows another tenet of great books: it credits previous work. Several times in the text Kong says where he learned a technique or what code he's modifying to do his bidding. This should serve as an example to other technical authors. Kong also does not treat his subject matter as a dark art practiced by people in long black coats at Def Con. He is professional and mentions where certain techniques like run-time kernel memory patching are used by commercial operating systems for "hot patching," as happens with Windows.
I have nothing bad to say about this book, although to get the absolute full learning experience it helps to know C programming, some assembly, and FreeBSD kernel internals. The Design and Implementation of the FreeBSD Operating System by McKusick and Neville-Neil (another excellent book) is helpful preparatory reading. The fact that Kong provided all of his source code for download is also very much appreciated. Bravo! I look forward to your next book.