Blocking a certain IP address with iptables
To block an ip address from accessing your linux box, you can use the following iptables rule:
iptables -A INPUT -s 222.124.24.131 -j DROP
If you just need to block a certain port (i.e. port 22 for SSH), you would do it like so:
iptables -A INPUT -s 222.124.24.131 -p tcp --destination-port 22 -j DROP