This part of the book discusses issues that arise when organizational networks are interconnected with the Internet. It also discusses ways of increasing your security through better programming.

• Chapter 21, Firewalls, describes how to set up various types of "firewalls" to protect an internal network from an external attacker.

• Chapter 22, Wrappers and Proxies, describes a few common wrapper and proxying programs that help protect your machine and the programs within it without requiring access to source code.

• Chapter 23, Writing Secure SUID and Network Programs, describes common pitfalls when writing your own software. It gives tips on how to write robust software that will resist attack from malicious users.