netfilter/iptables project
Firewall
Safing Portmaster
Portmaster is a free and open-source application that puts you back in charge over all your computer's network connections. Increase your privacy and security. Get peace of mind.
OPNsense - open-source firewall
IPFire
IPFire is a hardened, versatile, state-of-the-art Open Source firewall based on Linux.
SmoothWall
pfSense - FOSS firewall
pfSense is a free and open source firewall and router that also features unified threat management, load balancing, multi WAN, and more