Stephen Northcutt, Lenny Zeltser, Scott Winters, Karen Kent Frederick, & Ronald W. Ritchey. (2003). Inside network perimeter security: The definitive guide to firewalls, VPNs, routers, and intrusion detection systems. Pearson Education.

Stephen Northcutt, Lenny Zeltser, Scott Winters, Karen Kent Frederick, and Ronald W. Ritchey. Inside Network Perimeter Security: The Definitive Guide to Firewalls, VPNs, Routers, and Intrusion Detection Systems. New Delhi: Pearson Education, 2003.

Stephen Northcutt, et al. Inside Network Perimeter Security: The Definitive Guide to Firewalls, VPNs, Routers, and Intrusion Detection Systems. Pearson Education, 2003.