Université Catholique de Louvain: Olivier Bonaventure's "Computer Networking: Principles, Protocols, and Practice"
Read "Firewalls" on pages 166-168. Stop at "NAT," which you will read below. As you read, consider the following questions: When you first used your computer to access the Internet, what was the first security technique you heard about? How does a firewall protect your system from the "evil-doers" lurking on the Internet?