Today we’ll show you how to block ip address using iptables. In the following article we are adding a blacklist to the firewall script which will allow you to block any abusive IP addresses or ranges of IPs in your Debian or Ubuntu based virtual server. Iptables is a user space application program that allows a system administrator to configure the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores. Blocking an IP address using iptables is fairly easy task and it should take no more then 5 minutes.