Defining The Iptables Rule
Decide which packets you want filtered.
Lets filter all ICMP packets coming through the loopback interface:
iptables -I INPUT 1 --in-interface lo --proto icmp --jump QUEUE
(the '-I ... 1' inserts this as the first filtering rule).
By default, matching packets will be discarded, until we have a program listening for them.
Originally written by