Chapter 1. Introduction to Firewalls

Depending on whom you talk to, a firewall is either the cornerstone of their organization's security infrastructure, or it is a device that has woefully failed to live up to expectations. How can one device have such a contrast in perceptions? The biggest reason for this is a misunderstanding of what a firewall is and is not, and what a firewall can and cannot do.

This chapter looks at what a firewall is and how a firewall works to illustrate what are the reasonable expectations for a firewall. This chapter also examines the threats that exist and motivations of attackers to explore how firewalls canand most important, cannotprotect against those threats.