Introduction

This question is asked consistently on Ubuntu Forums. I am hoping that I can create something of a generally accepted answer that contains all the necessary links to appropriate resources.

What firewall does Ubuntu have?

iptables documentation

ufw documentation

I have no open ports, so I don't need a firewall, right?

Article demonstrating how different types of firewall rules can be bypassed by an attacker.

Strong Outbound Rules for UFW Strong Outbound rules using UFW, GUFW or iptables

You just said I have no services listening so then how can an application become compromised?

Apparmor forum sticky

Well, I'm behind a NAT router so none of this is for me, right?

Additional Resources :

Ubuntu Forums Security Sticky

Originally posted The Ubuntu Forums (ubuntuforums.org)

DoINeedAFirewall (last edited 2012-07-09 16:16:23 by host-89-242-244-187)