Install Fail2Ban on Ubuntu and CentOS

Ubuntu

Install Fail2Ban.

sudo apt-get update  
sudo apt-get install fail2ban  

Review configuration at /etc/fail2ban/jail.conf to see if you want to modify any default values.

Create a local jail config as below:

vim /etc/fail2ban/jail.local  

with the following contents:

[ssh-iptables]

enabled  = true  
filter   = sshd  
action   = iptables[name=SSH, port=ssh, protocol=tcp]  
logpath  = /var/log/secure  
maxretry = 5  

Start Fail2Ban service:

sudo service fail2ban start  

To see which IPs are blocked:

iptables -L -n  

CentOS

Install Fail2Ban.

yum install epel-release  
yum install fail2ban  

Review configuration at /etc/fail2ban/jail.conf to see if you want to modify any default values.

Create a local jail config as below:

vim /etc/fail2ban/jail.local  

with the following contents:

[ssh-iptables]

enabled  = true  
filter   = sshd  
action   = iptables[name=SSH, port=ssh, protocol=tcp]  
logpath  = /var/log/secure  
maxretry = 5  

Start Fail2Ban service:

chkconfig --level 23 fail2ban on  
service fail2ban start  

To see which IPs are blocked:

iptables -L -n