Description: Linux kernel 2.4+ iptables administration tools\n netfilter and iptables provide a Linux kernel framework for\n stateful and stateless packet filtering, network and port addresss\n translation, and other IP packet manipulation. The framework is the\n successor to ipchains.\n \n netfilter and iptables are used in applications such as Internet\n connection sharing, firewalls, IP accounting, transparent proxying,\n advanced routing and traffic control.\n \n iptables web site: [link|http://www.iptables.org/|http://www.iptables.org/]
That's on my Ubuntu box (tracking Breezy). What's yours say?
To answer your question: iptables is the current state of the art in Linux firewalling.