SmoothWall is a best-of-breed Internet firewall/router, designed to run on commodity hardware, and to give an easy-to-use administration interface to those using it. Built using open source and Free software, it's distributed under the GNU Public Licens

SmoothWall Express is an open source firewall distribution based on the GNU/Linux operating system.
Linux is the ideal choice for security systems; it is well proven, secure, highly configurable and freely available as open source code.

SmoothWall includes a hardened subset of the GNU/Linux operating system, so you don't have to install any separate OS.

Designed for ease of use, SmoothWall is configured via a web-based GUI, and requires absolutely no knowledge of Linux to install or use.

Smoothwall Feature List
Hardware support:
1. Any Pentium class CPU and above - with a recommended minimum of 128MB RAM
2. 64bit build for Core 2 systems

Firewalling:
1. Supports LAN, DMZ, and Wireless networks, plus Extrnal.
2. External connectivity via: Static Ethernet, DHCP Ethernet, PPPoE, PPPoA using various USB and PCI DSL modems.
3. Portforwards, DMZ pin-holes
4. Outbound filtering
5. Timed access
6. Simple to use Quality-of-Service (QoS)
7. Traffic stats, including per interface and per IP totals for weeks and months
8. IDS via automatically updated Snort rules
9. UPnP support
10. List of bad IP addresses to block

Proxies:
1. Web proxy for accelerated browsing
2. POP3 email proxy with Anti-Virus
3. IM proxy with realtime log viewing

UI:
1. Responsive web interface using AJAX techniques to provide realtime information
2. Realtime traffic graphs
3. All rules have an optional Comment field for ease of use
4. Log viewers for all major sub-systems and firewall activity

Maintenance:
1. Backup config
2. Easy single-click application of all pending updates
3. Shutdown and Reboot from UI

Other:
1. Time service for network
2. Develop SmoothWall yourself using the self-hosting "Devel" builds.

The license of this software is Free, you can free download and free use this firewall software.