Install ufw by entering the following commands in the terminal:
sudo apt update sudo apt install ufw
Description:
program for managing a Netfilter firewall
The Uncomplicated FireWall is a front-end for iptables, to make managing a Netfilter firewall easier. It provides a command line interface with syntax similar to OpenBSD's Packet Filter. It is particularly well-suited as a host-based firewall.
Homepage: https://launchpad.net/ufw
Version: 0.35-5
Section: admin