Uncomplicated FireWall (UFW)

Linux

@see UFW wikipedia, UFW setup tutorial UFW common rules and commands

The Uncomplicated Firewall (UFW) is a frontend for iptables and is particularly well-suited for host-based firewalls. UFW provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall. UFW aims to provide an easy to use interface for people unfamiliar with firewall concepts, while at the same time simplifies complicated iptables commands to help an administrator who knows what he or she is doing.

Installation

UFW is available by default in all Ubuntu installations since 8.04 LTS and in all Debian installations since 10. However, UFW can be installed using the following command:

sudo apt install ufw

To check the status of UFW run the following command:

sudo ufw status

Run the following commands to enable and disable the firewall respectively:

sudo ufw enable

sudo ufw disable

Configuration

The default configuration in UFW is to deny all incoming connections and allow all outgoing connections, to change this you use the following commands:

sudo ufw default deny incoming

sudo ufw default allow incoming

sudo ufw default allow outgoing

sudo ufw default deny outgoing

To allow connections to a service that runs in its default port and appears in the /etc/services file (for example ssh) run the following command:

sudo ufw allow ssh

If the service is not running in its default port or it does not appear in the /etc/services file you can enable connections to a specific port by running the following command:

sudo ufw allow [port]

To block incoming traffic on a specific port run the following command:

sudo ufw deny [port] 

To delete a rule use the following command:

sudo ufw delete [rule_number]

To find the number associated with a rule run the following command:

sudo ufw status numbered

To set a rate limit of incoming connections on a specific port (this might help prevent DoS attacks) run the following command:

sudo ufw limit [port]