Bonus 3 :

--> Set up a service of your choice that you think is useful (NGINX / Apache2 excluded!). During the defense, you will have to justify your choice.

Fail2Ban tool:

"To enhance the security of SSH and prevent unauthorized access attempts."

I_ Installation :

$ sudo apt-get update
$ sudo apt-get install fail2ban

II_ Configuration:

$ cd /etc/fail2ban/
$ sudo nano jail.local
--> Add or modify the SSH section to define the rules inside jail.local:
[ssh]
enabled = true
port = ssh # Use the actual SSH port if it's different from default
filter = sshd
logpath = /var/log/auth.log
maxretry = 3 # Number of failed login attempts allowed before banning
bantime = 3600 # Ban duration in seconds (adjust as needed)

III_ Restart Fail2Ban:

$ sudo systemctl restart fail2ban