Network Security Bible, 2nd Edition

Chapter 18. Firewalls

IN THIS CHAPTER

• Understanding the importance and use of a firewall

• Determining the different types of firewalls

• Identifying how to configure a firewall

Prevention is a key to stopping an attacker. We want to prevent as many attacks as possible, and when we can't prevent an attack we want to detect it as soon as possible. On most networks firewalls are the main method of preventing attacks. Therefore it's important to understand how to design and configure a firewall to provide the highest degree of security possible.

This chapter will explore the different types of firewalls and critical rules that need to be applied when using a firewall. A firewall will be effective only if it is designed and configured correctly.

Firewalls

There are many reasons for an organization to employ firewalls to secure its networks from other, insecure networks.

• Poor authentication—Most network services and applications do not directly use authentication and encryption features, as they could be too cumbersome or costly. When such applications are accessed from the outside, the applications themselves may not be able to distinguish between legitimate and fake users.

• Weak software—Most purchased software and free software, known as freeware (many of the commonly used remote login, file transfer, and e-mail programs), are not optimized for security features. Using them could create vulnerabilities in the respective networks. A firewall can be highly effective in scanning and logging Internet ...