Binary package “iptables” in ubuntu lucid
administration tools for packet filtering and NAT
These are the user-space administration tools for the Linux
kernel's netfilter and iptables. netfilter and iptables provide
a framework for stateful and stateless packet filtering, network
and port address translation, and other IP packet manipulation.
The framework is the successor to ipchains.
netfilter and iptables are used in applications such as Internet
connection sharing, firewalls, IP accounting, transparent proxying,
advanced routing and traffic control.