Part I explores the problem of Internet security and focuses on firewalls as one very effective piece of the solution to that problem

Chapter 1, Why Internet Firewalls? , introduces the major risks associated with using the Internet today, discusses what you're trying to protect and what you're trying to protect it against, discusses various security models, and introduces firewalls by discussing what they can and can't do for your site's security.

Chapter 2, Internet Services , outlines the services users want need from the Internet and the security problems posed by those services.

Chapter 3, Security Strategies , outlines the basic security principles that an organization needs to understand before it adopts a security policy and invests in specific security mechanisms.