How to enable ufw on your server
If you are on Ubuntu, your in luck: it's already there, otherwise install it with "apt-get ufw".
The first and most important thing if you are only connected via SSH: Don't lock yourself out!
Before starting the firewall make sure to open the most basic standard ports for ssh, http and https and deny all the rest:
ufw allow 22
ufw allow 80
ufw allow 443
ufw default deny
Only after this you may proceed to actually start the firewall with
Of course "disable" is the opposite and stops the firewall again. Btw: enable/disable also register ufw to be started/not be started on boot.
To activate verbose logging to /var/log/syslog, enter
ufw logging on
You can have a look at applications that registered themselves automatically to ufw with
ufw app list