The open source community has contributed many popular and useful security tools, including these four great router/firewall projects. This list was assembled by our colleagues at our sister site, LinuxPlanet and includes projects that offer a stateful inspection firewall and NAT, among other things.

The LinuxPlanet list includes two Linux-based projects and two based on FreeBSD. Collectively, they've received more than one million downloads.

One began six years ago as a fork of the m0n0wall project. It can be used in homes or in large corporations and organizations. It's available as a Live CD, hard drive installation, or embedded.

One provides a captive portal, SVG-based traffic graphing, SNMP agent, DynDNS client, and a Wake on LAN client, among other things.

Another delivers application-level proxies for numerous protocols (HTTP, FTP, POP3, SMTP) with antivirus support. It can also perform virus and spam-filtering for email traffic (POP and SMTP) and do Web content filtering.

And the fourth runs on any Pentium class CPU and above. It is designed with home and small business users in mind.

To find out which router/firewall projects LinuxPlanet recommends, read the full story here.