Firewalls are essential to every organistaion. Apart from the expensive commercial ones, there exist numerous open source counterparts. It is usually difficult to choose the best open source Firewall that suits your needs. So here is a list of the most popular and best Open Source Firewall alternatives.

1. SmoothWall

SmoothWall is a Linux distribution designed to be used as an open source firewall. Designed for ease of use, SmoothWall is configured via a web-based GUI, and requires little or no knowledge of Linux to install or use.

2. FireHOL

FireHOL is a stateful iptables packet filtering firewall configurator. It is abstracted, extensible, easy and powerful. It can handle any kind of firewall, but most importantly, it gives you the means to configure it, the same way you think of it.

3. Firestarter

Firestarter is an Open Source visual firewall program. The software aims to combine ease of use with powerful features, therefore serving both Linux desktop users and system administrators. Linux security does not have to be complex, and simplicity does not have to mean sacrificing power. With Firestarter you will have a firewall up and running in minutes.

4. NetDefender

NetDefender is a Free Firewall with source code, which can be downloaded along with firewall executables. Netdefender works on windows 2000 and windows XP.

5. Endian Firewall

Endian Firewall Community is an all-in-one Linux security distribution that turns every system into a full featured security appliance. Designed with usability in mind, Endian developed a solution that is extremely flexible, easy to install and manage. The Community version has been warmly embraced by the open source community and has so far enjoyed over 330000 downloads with thousands of installations worldwide.