How to block a specific IP address?

To block an individual IP address from accessing your Linux server, you can use the following iptables command:

iptables -A INPUT -s IPADDR -j DROP

Simply replace IPADDR with the IP address you are wanting to drop all packets from.

How to block ranges?

Here is an example of a range block:

iptables -A INPUT -s 192.168.0.1/24 -j DROP

This would block 192.168.0.1-255

How to unblock the IP?

Simply change "DROP" in the commands above to "ACCEPT".