Quick instructions for enabling firewall on Ubuntu using Uncomplicated Firewall (ufw). The resulting rules are quite obvious. Incoming traffic is denied, except for ssh, http and https (these refer to /etc/services) and outgoing is allowed.
These policies do not affect ICMP. Incoming ICMP remains allowed as per default ufw settings.
sudo apt-get install ufw sudo ufw allow ssh sudo ufw allow http sudo ufw allow https sudo ufw default deny incoming sudo ufw default allow outgoing sudo ufw enable