Shorewall gateway/firewall configuration tool makes it possible to use much easier rules and takes a burden of translating it to iptables language and maintaining it.
Rope is a programming language that allows developers to write extensions to the Iptables/Netfilter components of Linux using a simple scripting language based on Reverse Polish notation.
Rusty Russell started the netfilter/iptables project in 1998; he had also authored the project's predecessor, ipchains.
NETLINK NFLOG provides an interface used to communicate between used Netfilter and iptables.