• https://www.digitalocean.com/community/tutorials/recommended-security-measures-to-protect-your-servers
• https://linuxize.com/post/how-to-change-hostname-on-ubuntu-18-04/
• https://www.osetc.com/en/how-to-allow-or-deny-ssh-root-login-in-linux.html
• https://ubuntuhandbook.org/index.php/2013/07/disable-ping-response-ubuntu-server/