Collections strong in web design and programmer's guides know that rootkits have a negative image - but DESIGNING BSD ROOTKITS provides all the information on how to overcome any bad image and problems to develop effective rootkits under the FreeBSD operating system. This instructional is actually a tutorial, so it may also be used in programming classes: it explains how to maintain root access and how to hack Free BSD, using many examples which assume no prior kernel-hacking knowledge. Code is described, analyzed, and linked to real-world scenarios for maximum understanding, making for a perfect programmer's guide.

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.

--- DISCLAIMER: This is a requested review by No Starch Press, however any opinions expressed within the review are my personal ones. ---


This enjoyable readable book gradually and very systematically evolves around hacking the kernel of a BSD system.

Chapter 1: Loadable Kernel Modules 22p.
Chapter 2: Hooking 13p.
Chapter 3: Direct Kernel Object Manipulation 20p.
Chapter 4: Kernel Object Hooking 4p.
Chapter 5: Run-Time Kernel Memory Patching 27p.
Chapter 6: Putting It All Together 26p.
Chapter 7: Detection 8p.

Its written in a style that allows also non-developers to grasp the main procedures and steps involved for modifying a systems kernel (assuming the attacker got access to a privileged system account).

Chapters 1 to 5 explain the several methods for modifying the kernel.

While the book is divided into 7 chapters, its most value really is the Chapters 6 which has many of those WoW effects included.

All or most technics described of chapters 1-5 will be used in chapter 6 for show casing how to circumvent an HIDS. Here is where all learned technics finally come all together.

So the reader dabbles with the author from an initial "simple" idea of bypassing an HIDS from one issue to the next. First the system call is hooked, so technically its kind of working, but then we realize that in order to make it perfect we need to hide the just created file (which contains the execution redirection routine). So the next obvious step is to hide the file so we dont leave a footprint on the system, just to realize that we need to hide the KLD (Dynamic Kernel Linker). So now everything is hidden but we forgot about the change of the /sbin directories access/ modification and change time, so we have to go after that too...

Its technically very interesting to learn how the author approaches the issues involved in order to avoid being detected by the HIDS or commands the user might use. That the author is technically on top of things is also shown f.e. by some info included in the book which is already referring to FreeBSD 7.

To get the most out of the book you ideally have programming knowledge of C, assembly etc. and debugging software systems. So I think its most valuable to system administrators, developers and security consultants.

I don't do a lot with BSD nowadays.. a lot of software customers want is only for Linux, and although sometimes it could be ported, the customers seem to want Linux. However, I cut my teeth on old SunOS, so bsdisms are familiar and friendly to me.

Working through this book was fun and informative. You can download sources from [....]

The concepts apply equally well to Linux, of course, and I also realized that some of the areas explored come up in ordinary application work and especially in system troubleshooting, so this isn't entirely about subverting systems for evil purpose.