Chapter 2. Firewall Basics

This chapter covers the basics of firewalls. Firewalls can be distinguished in a variety of ways: from the size of the network they are designed to operate in to the way they provide protection. This chapter examines the basic taxonomy of firewalls and uses the convention of classifying firewalls based on "size"personal or desktop firewalls, small office/home office (SOHO) firewalls, and enterprise-level firewalls. In addition, this chapter discusses the various ways firewalls defend the networks they are placed in, from simple packet filters to stateful packet filters to application proxies.

This chapter provides a high-level overview of the various firewall products discussed throughout the book.