Comodo Firewall

Comodo Firewall Pro - Secure your system against internal attacks such as Trojan viruses / malicious software and external attacks by hackers.

Free Windows

Little Snitch

Little Snitch is a firewall application that monitors and controls outbound internet traffic.

Commercial

Radio Silence

Radio Silence lets you block individual apps from accessing the internet. It never throws pop-ups on the screen, and is completely invisible.

Commercial Mac OS X

netfilter

Netfilter software comprises iptables, ipset, conntrack-tools, libnetfilter and more. It is the core of Linux firewalls and NAT. It consists of a set of hooks inside the Linux kernel and a number of utilities to manage callback functions.

Free Open Source Linux

Murus Firewall

Murus is a frontend for the OS X PF network firewall. From basic filtering to advanced proactive options, Murus allows to easily configure a complex network setup dragging and dropping icons and moving sliders and selecting checkboxes.

Freemium Mac OS X

Rubbernet

Rubbernet keeps an eye on all network-enabled apps running on your Mac. It provides real-time monitoring so you can keep an eye on the exact state of your live network connections.

Freemium Mac OS X

LuLu by Objective-See

LuLu is the free open-source macOS firewall that aims to block unauthorized (outgoing) network traffic.

Free Open Source Mac