15. Ubuntu Firewall Basics

A firewall is a vital component in protecting an individual computer system or network of computers from external attack (typically from an internet connection). Any computer connected directly to an internet connection should ideally run a firewall to protect against malicious activity. Similarly, any internal network must have some form of firewall between it and an external internet connection.

Ubuntu is supplied with powerful firewall technology known as iptables built-in. Entire books can, and indeed have, been written about configuring iptables. If you would like to learn about iptables we recommend:

https://www.linuxtopia.org/Linux_Firewall_iptables/index.html

The goal of this chapter is to cover some of the basic concepts of firewalls, TCP/IP ports and services. The configuration of a firewall on an Ubuntu system will be covered in “Using gufw and ufw to Configure an Ubuntu Firewall”. For more complex firewall requirements...