Install & setup a firewall

This document will help you install and configure a UFW firewall to secure incoming connections to your server. We will detail here the basics to customize over the tutorials available on this blog.

Sommaire du tutoriel

• 0. Prerequisite

• 1. Installation

• 2. Configuration

Prerequisite

Before starting this tutorial, please carefully read the following prerequisites :

• Setup SSH connection

1. Installation

Connect in SSH to the server.

Then let’s start by updating our server :

    > sudo apt-get -y update && sudo apt-get -y upgrade && sudo apt-get autoremove

Then install the UFW firewall package :

    > sudo apt install -y ufw

2. Configuration

In our base configuration, we will disallow all incoming connections

    > sudo ufw default deny incoming

Then we will only allow connections to the SSH port (here port 22123)

    > sudo ufw allow 22123/tcp

To validate the configuration run the command :

    > sudo ufw enable

To check the status of your firewall :

    > sudo ufw status verbose

If all went well, this last command should print :

    Status: active
    Logging: on (low)
    Default: deny (incoming), allow (outgoing), disabled (routed)
    New profiles: skip
    
        To                         Action      From
        --                         ------      ----
        22123/tcp                  ALLOW IN    Anywhere
        22123/tcp (v6)             ALLOW IN    Anywhere (v6)