Linux Babe published a tutorial about using UFW Firewall on Debian, Ubuntu, and Linux Mint.

How to Use UFW Firewall on Debian, Ubuntu, Linux Mint

This tutorial is going to show you how to use UFW (Uncomplicated FireWall) on Debian/Ubuntu/Linux Mint with some real-world examples. Managing firewall is a basic skill that every system admin needs to know. This article intends to get the reader started with UFW, but does not explore the ins and outs of UFW.

How to Use UFW Firewall on Debian, Ubuntu, Linux Mint