iptables -A INPUT -s 127.0.0.1 -p icmp -j DROP
SS The above is the original page content for iptables, not very useful ;) btw, the above command will create a rule to DROP every ICMP packet received with source address of 127.0.0.1.
What is iptables? The firewalling framework of the Linux kernel version 2.4 and 2.6, it replaced ipchains present in <= 2.2 version.