Linux® Bible, 2008 Edition: Boot Up to Ubuntu®, Fedora®, KNOPPIX, Debian®, openSUSE®, and 11 Other Distributions

Chapter 18. Running a Linux Firewall/Router

IN THIS CHAPTER

• Understanding firewalls

• Protecting desktops with firewalls

• Managing firewalls with iptables

• Making a Coyote Linux bootable firewall floppy

• Getting other bootable firewalls

The Internet is a potentially hostile place, so you need to be able to protect your computer from attacks coming in from the Internet. One essential element of security for Internet-facing computers is a firewall. A firewall can protect your computer or private network from outside intruders. Placing a firewall on the route between your local network and the Internet gives you tremendous power and flexibility to manage your network traffic. You can react to every packet coming in or going out of your network based on where it's from, where it's going, and what it is requesting to do.

Linux is often used as a firewall. In fact, several Linux distributions are configured to act exclusively as a firewall (running on media as small as a floppy disk). Because firewall tools can also be used to protect personal desktop systems, several Linux distributions include graphical tools for managing firewalls in an appropriate way for desktops. So, in effect, almost any Linux distribution can be used as a dedicated firewall or can simply be configured to use firewall features to protect itself from unwanted outside access.

In this chapter, you explore the features used in nearly every Linux system today for creating firewalls (using iptables features) and discover how to use ...