Setting up UFW

UFW stands for uncomplicated firewall. So basically, UFW is a simple and efficient firewall to your Linux.

Install UFW to Debian

sudo apt install ufw

Install UFW to Arch Linux

sudo pacman -S ufw

Setup the default policies

sudo ufw default deny incoming
sudo ufw default allow outgoing

Allow SSH

sudo ufw allow ssh

or

sudo ufw allow 22

It’s really important to allow SSH, because in the worst case, you log yourself out and you can’t login again, because the incoming traffic is blocked.

Enable UFW

sudo ufw enable

or

sudo systemctl start ufw
sudo systemctl enable ufw

Source(s):

• Digitalocean