Book Review – Extrusion Detection

Security Monitoring for Internal Intrusions







Rating *****

Despite being over six years old now, this book is certainly not outdated in the slightest. While most network security books and guides would focus on perimeter defence from outsider threats, Bejtlich concentrates on attacks launched within the organisation. At the time of publishing, this book was unique in its approach to defensive practices and is aimed to go hand in hand with Bejtlich’s ‘Tao of Network Security’, picking up where Tao left off and concentrating solely on defence, where Tao started from the point of view of the attacker.

First thing to notice about this book is the foreword by Marcus Ranum, which, unusual to most books, consists of an interview with the author and highlights how different Extrusion Detection is from other Network Security Guides.

The book is aimed at all those who have an intermediate to advance knowledge of network security and so should be used by those just starting out in the industry, especially as Bejtlich talks about tools and techniques that, at the time of writing, were not common practices amongst professionals. However, it holds great potential value as an addition to anyone’s security/information assurance library.

Traditionally, the main focus of network security has been about keeping the hackers and malicious users out. The book is split into three specific sections, Detecting and Controlling Intrusions, Network Security Operations and Internal Intrusions, taking the reader on a journey from the reasons to look for Extrusions through to the various types of Extrusion, such as Malicious IRC Bots. Bejtlich uses various technologies, such as Proxies and IDS/IPS, as demonstrations using commands that can easily be adapted into organizations’ own technologies.

To those specifically interested in Network Forensics, Bejtlich devotes an entire chapter to just this and discusses the links between the security practices discussed throughout the book and the forensics practices used within the chapter. Incident Response is also explained prior to Forensics. Bejtlich gives a detailed introduction to Network Forensics and describes it as being different from Digital Forensics in that it is focused on Packet Capture, using tools such as Wireshark/Ethereal. The emphasis here, however, is the Network Forensics is a valuable and crucial part in the defence of a network infrastructure both from internal and external threats.

Followers of Richard Bejtlich’s Tao security blog will instantly recognise his unique method of describing and demonstrating the various tools and techniques required to put Extrusion Detection into practice. Throughout the book there are valuable diagrams, screenshots and actual packet captures that help the reader to fully understand each point that is made, a feature that is often overlooked in many security guides.


This book is a valuable read for anyone interested, or working, in the security and forensics industry. Betjlich provides a refreshing approach to defensive methods and illuminates the potential damage of insider threats. Highly recommended as a partner guide to ‘The Tao of Network Security’, which together provide an ultimate guide to Network Security.

Reviewer Name:   Willem Knot

Book Title:   Extrusion Detection

Book Subtitle:   Security Monitoring for Internal Intrusions

Author(s):   Richard Bejtlich (Foreword by Marcus Ranum)

Publisher:   Addison-Wesley

Date of Publishing:   8th November 2005

ISBN-13: 978-0321349965

Price: £39.99 (UK), $54.99 (USA)