Chapter 3: Installing Firewalls and Filters

Overview

Many network managers have an intense dislike for firewall and network filtering technologies. This is not surprising given the complexities and the prevalence of conflicting beliefs regarding firewall design and implementation.

This chapter steps you through the following tasks :

Identify firewall rules that may be present before you make changes
Understand the difference between firewall rules and network filters
Identify the level and type of protection necessary for your system
Install minimum protective measures to ensure the system s safety

Before moving on, take stock:

The Linux operating system has been installed and is operational.
Nonessential services have been turned off or disabled. A service that has been turned off will restart the next time the system is restarted (or when the runlevel changes). A service that has been disabled will not restart when the system is restarted or when the runlevel is changed.
There are many areas of vulnerability to be addressed immediately ”you must get ready to take the steps that are outlined in the chapters that follow this one.