TinyWall - Lightweight and non-intrusive firewall
ufw - Ufw stands for Uncomplicated Firewall, and is program for managing a netfilter firewall.
Emsisoft Online Armor Firewall - Emsisoft Online Armor Firewall is a freemium online firewall protection system by the Emsisoft that is based on the own independent protection technology of the Emsisoft.
LuLu by Objective-See - LuLu is the free open-source macOS firewall that aims to block unauthorized (outgoing) network...
Windows Firewall Control - Windows Firewall Control is not the built in firewall system in the Windows operating systems.
Plasma Firewall - Plasma Firewall is an open-source control panel with which you can manage your system firewall.