Fail2ban

https://www.digitalocean.com/community/tutorials/how-to-protect-an-apache-server-with-fail2ban-on-ubuntu-14-04

sudo apt-get update
sudo apt-get install fail2ban

[sshd]

# To use more aggressive sshd modes set filter parameter "mode" in jail.local:
# normal (default), ddos, extra or aggressive (combines all).
# See "tests/files/logs/sshd" or "filter.d/sshd.conf" for usage example and details.
#mode   = normal
enabled = true
mode = aggressive
publickey = any
port    = ssh
maxretry = 3
findtime = 300
bantime = 3h
logpath = %(sshd_log)s
backend = %(sshd_backend)s


Bunch of request 
while true; do ssh root@IP 2>&1; sleep 1; done


For example, to remove an IP address jailed within ssh, use the below command.

sshd will be jail name 
fail2ban-client set sshd unbanip IP
fail2ban-client set sshd unbanip IP