I've currently 3 servers with SSH service being attacked by brute force. The attack is from multiple sources or one who's changing his IP with each attempt performed.
I need help to stop current attacks and protect/prevent from future ones.
I've already setup fail2ban in one machine after following (quickly) this guide: How to protect SSH with Fail2Ban on Ubuntu 14.04 but I haven't saw any improvements by doing so.
Please, I really need help on this as there are sensitive services running in every machine which can not go down and these attacks are sucking machines' resources.
Thanks in advance, best regards.
P.S.: I know there are several questions/answers on this topic but couldn't find any suitable answer to help me...