This unique book represents the first rigorous and comprehensive study of firewall policy design and analysis. Firewalls are the most critical and widely deployed intrusion prevention systems. Designing new firewall policies and analyzing existing firewall policies have been difficult and error-prone. This book presents scientifically sound and practically useful methods for designing and analyzing firewall policies. This book is useful to a variety of readers. First, it can be used as a handbook for network/firewall administrators and network security professionals. Second, it can be used as an advanced textbook for graduate students and senior undergraduate students in computer science and engineering. Third, it is also suitable for non-experts in network security who wish to understand more about firewalls. The presentation of the book is detailed enough to capture the interest of curious readers, and complete enough to provide the necessary background material needed to delve further into the subject of firewalls and network security.