Gufw might be a bit more popular than netfilter. We know about 1 link to it since March 2021 and only 1 link to netfilter. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
The netfilter subsystem handles this, it's part of the Linux Kernel and part of all linux distros that don't use a custom kernel. You can read more about it here. Source: about 3 years ago
2- You should set it up anyways gufw.org. Source: about 3 years ago
Murus Firewall - Murus is a frontend for the OS X PF network firewall.
TinyWall - Lightweight and non-intrusive firewall
Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
ufw - Ufw stands for Uncomplicated Firewall, and is program for managing a netfilter firewall.
Windows 10 Firewall Control - Windows 10 Firewall Control: simple and exhaustive solution for applications network activity controlling and monitoring.
NetLimiter - NetLimiter is an ultimate Internet traffic control and monitoring tool designed for Windows.