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.