OpenSnitch is a GNU/Linux port of the Little Snitch firewall
OWASP Coraza WAF is a golang modsecurity compatible firewall library
iptables mini-script in file-wizard
CacheGuard Gateway is a UTM, a WAF, and a QoS management appliance.
Web application firewall in C language uses libevent
OWASP ModSecurity Core Rule Set (CRS) Project
Bash script to enable the firewall on startup of your Ubuntu server.
Jateway is a general purpose TCP/IP connection proxy
network control and reporting
KnockIt! is a port Knocking tool for MAC OSX
Lomalarga is a VPN-like service based on SSH and Linux.