TinyWall - Lightweight and non-intrusive firewall
Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
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.
Radio Silence - Radio Silence is a network monitor and firewall for the macOS. The software stops apps from making network connections. The firewall runs in the background and does not require an open window.