How To Install DenyHosts on Ubuntu 16.04 LTS

In this tutorial, we will show you how to install and configure DenyHosts on Ubuntu 16.04 LTS. For those of you who didn’t know, DenyHosts is a log-based intrusion prevention security tool for SSH servers written in Python. It is intended to prevent brute-force attacks on SSH servers by monitoring invalid login attempts in the authentication log and blocking the originating IP addresses. Due to the simplicity of DenyHost and the ability to manually configure your rules it is widely used as an alternative to Fail2ban which is a bit more complicated to use and configure. DenyHosts unfortunately does not support IPv6.

This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you the step-by-step installation DenyHosts on a Ubuntu 16.04 (Xenial Xerus) server.

Prerequisites

• A server running one of the following operating systems: Ubuntu 16.04 (Xenial Xerus).
• It’s recommended that you use a fresh OS install to prevent any potential issues.
• SSH access to the server (or just open Terminal if you’re on a desktop).
• A non-root sudo user or access to the root user. We recommend acting as a non-root sudo user, however, as you can harm your system if you’re not careful when acting as the root.

Install DenyHosts on Ubuntu 16.04 LTS

Step 1. First, make sure that all your system packages are up-to-date by running the following apt-get commands in the terminal.

sudo apt-get update
sudo apt-get upgrade

Step 2. Installing DenyHosts on Ubuntu 16.04.

Install the DenyHosts package using apt-get command:

sudo apt-get install denyhosts

Step 3. Configure DenyHosts.

Once the Denyhosts are installed, make sure to whitelist your own IP address, so you will never get locked out. To do this, open a file /etc/hosts.allow:

sudo nano /etc/hosts.allow

Below the description, add each IP address one by one on a separate line, that you never want to block. The format should be as follows:

# hosts.allow   This file contains access rules which are used to
#               allow or deny connections to network services that
#               either use the tcp_wrappers library or that have been
#               started through a tcp_wrappers-enabled xinetd.
#
#               See 'man 5 hosts_options' and 'man 5 hosts_access'
#               for information on rule syntax.
#               See 'man tcpd' for information on tcp_wrappers
#
sshd: 114.124.37.154
sshd: 114.121.131.131
sshd: 172.16.25.156

You can further configure any settings in the DenyHosts.conf file by going to the following and updating according to your preference:

sudo nano /etc/denyhosts.conf

Save your work and restart DenyHosts by running the commands below:

systemctl restart denyhosts.service
systemctl enable denyhosts.service

View DenyHosts logs:

tail -f /var/log/denyhosts
tail -f /var/log/secure

Congratulations! You have successfully installed DenyHosts. Thanks for using this tutorial for installing DenyHosts on Ubuntu 16.04 LTS  (Xenial Xerus) system. For additional help or useful information, we recommend you to check the official DenyHosts website.

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