Some useful info:
https://linux-notes.org/ustanovka-fail2ban/
https://github.com/Bebef/fail2ban-filter.d
https://stackoverflow.com/questions/19794107/fail2ban-error-can´t-ban-with-lighttpssd-auth
https://easyengine.io/tutorials/nginx/fail2ban/
Check who’s banned:
fail2ban-client status JAILNAME
fail2ban alerts sent to a Rocket.Chat channel:
https://forums.rocket.chat/t/fail2ban-and-rocket-chat-integration/2544