===== Fail2ban===== 
Install fail2ban and itset: 
<code bash>
apt-get install fail2ban ipset
</code> 
Copy config file to local one which has high propriety 
<code bash>
cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
</code>
Or create a new one:
<code bash>
vi /etc/fail2ban/jail.local
</code>
Replace <YOUR_SSH_PORT>:
<code bash>
[DEFAULT]
banaction = iptables-ipset-proto6-allports

[sshd]
enabled = true
port    = <YOUR_SSH_PORT>
logpath = %(sshd_log)s
backend = %(sshd_backend)s
maxretry = 3
findtime = 604800
# max is 4294967 for ipset timeout
bantime = 4294967


[sshd-ddos]
# This jail corresponds to the standard configuration in Fail2ban.
# The mail-whois action send a notification e-mail with a whois request
# in the body.
enabled = true
port    = <YOUR_SSH_PORT>
logpath = %(sshd_log)s
backend = %(sshd_backend)s
</code>
Restart fail2ban:
<code bash>
service fail2ban restart
</code>
Check status:
<code bash>
fail2ban-client status
fail2ban-client status sshd
</code>
Unban an IP:
<code bash>
fail2ban-client set sshd unbanip <IP>
</code>