LuLu is the free open-source macOS firewall
OpenSnitch is a GNU/Linux port of the Little Snitch firewall
Next Generation Open Source Firewall
OpenWRT ©VMWare ©ESXi Appliance NAT router
Web application firewall in C language uses libevent
A simple, portable port scanner
One of the most advanced DNS Proxy and DNS Firewall in one product.
A powerful network security tool, easy, safe and totally free.
Programmable completion code (bash) for ip[6]tables (netfilter.org)
PeerGuardian - a privacy oriented firewall application
360-FAAR Analyze FW1 Cisco Netscreen Policy Offline Using Config/Logs
Network Firewall Linux Kernel Module with Conflict Resolution Engine
Block or allow connections by country address blocks
Open source voucher management / hotspot system
KnockIt! is a port Knocking tool for MAC OSX
This tool locks down Linux and UNIX systems.
IoT Device, Gateway, Server platform
Personal firewall for linux desktop and android phone
A simple captive portal