Fail2ban

16 of september of 2023

Disclaimer: This post has been translated to English using a machine translation model. Please, let me know if you find any mistakes.

With Fail2ban we can block IPs that try to connect to one of our devices. Here I will explain how to configure the blocking when they attempt to connect via SSH.

Installation

The installation is very simple, we just have to do

sudo apt update
sudo apt install fail2ban

Configuration file

Once installed, we modify the configuration file by doing

sudo nano /etc/fail2ban/jail.conf

We go down to the part where it says [sshd], in my case I left it like this

[sshd]
bantime  = 172800    
port     = ssh
logpath  = %(sshd_log)s
backend  = %(sshd_backend)s
maxretry = 3

What it does is that if someone makes 3 connection retries, it bans that IP for 48 hours (172800 seconds).

Check the logs

We can check through the logs if any IP has been blocked with

cat /var/log/fail2ban.log

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