sudo nano /etc/ssh/ssh_config
Comment out the following lines
#GSSAPIAuthentication yes
#GSSAPIDelegateCredentials no
OR
sudo nano /etc/ssh/sshd_config
UseDNS no
UsePAM no # (Pluggable Authentication Modules)
PasswordAuthentication no # Heckers slow down the shits and create huge logs with continous bruteforce.