UFW can be used to set up firewall on Ubuntu server, that make sure only connections to certain services are allowed.
With UFW we can register different application profiles upon installation. These profile allow UFW to manage these applications by name.
OpenSSH is most commonly used application used to access server shell.
Registered profiles can be listed by running following command.
# ufw app list Output Available applications: OpenSSH
In order to access server shell, we need to allow SSH connections. SSH can be allow by running following command.
# ufw allow OpenSSH
Once OpenSSH is allowed, now let’s enable the firewall.
# ufw enable
y” and press
ENTER to proceed. You can see that SSH connections are still allowed by typing:
# ufw status Output Status: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6)
At the moment firewall blocks all the connections expect SSH, if you need to install and configure other services; remember to adjust firewall accordingly. For additional help take a look at "UFW Essentials" well written article by Mitchell Anicas at DigitalOcean community.