How to Configure a Firewall with UFW

UFW.sh

What is UFW? 
UFW, or uncomplicated firewall, is a frontend for managing firewall rules in Arch Linux, Debian or Ubuntu. UFW is used through the command line (although it has GUIs available), and aims to make firewall configuration easy (or, uncomplicated).

sudo apt-get update && sudo apt-get upgrade

#Install UFW
sudo apt-get install ufw

#Use UFW to Manage Firewall Rules. Set Default Rules
sudo ufw default allow outgoing
sudo ufw default deny incoming

#Add Rules. Rules can be added in two ways: By denoting the port number or by using the service name. For example, to allow both incoming and outgoing connections on port 22 for SSH.

#You can run:
sudo ufw allow ssh

#You can also run:
sudo ufw allow 22

#Similarly, to deny traffic on a certain port (in this example, 231) you would only have to run:
sudo ufw deny 231

#To further fine-tune your rules, you can also allow packets based on TCP or UDP. The following will allow TCP packets on port 80:
sudo ufw allow 80/tcp
sudo ufw allow http/tcp

#Whereas this will allow UDP packets on 1725:
sudo ufw allow 1725/udp

#Advanced Rules
To allow connections from an IP address:
sudo ufw allow from 204.61.107.0

To allow connections from a specific subnet:
sudo ufw allow from 204.61.107.0/24

To allow a specific IP address/port combination:
sudo ufw allow from 204.61.107.0 to any port 22 proto tcp

#Remove Rules

To remove a rule, add delete before the rule implementation. If you no longer wished to allow HTTP traffic, you could run:
sudo ufw delete allow 80

Deleting also allows the use of service names.

#Edit UFW’s Configuration Files
/etc/default/ufw
/etc/ufw/before.rules

#Check UFW Status
sudo ufw status

#Enable the Firewall
sudo ufw enable

#Disable the Firewall
sudo ufw disable

#Logging. You can enable logging with the command:
sudo ufw logging on

#Check log file
/var/logs/ufw

Good