1. IP packet filter administration From whatis

2. IP packet filter administration tools for 2.4.4+ kernels netfilter and iptables are the framework inside the Linux 2.4.x kernel which enable packet filtering, network address translation (NAT) and other packet mangling. netfilter is a set of hooks inside the linux 2.4.x kernel's network stack which allows kernel modules to register callback functions called every time a network packet traverses one of those hooks. iptables is a generic table structure for the definition of rulesets. Each rule within an IP table consists out of a number of classifiers (matches) and one connected action (target). netfilter, iptables and the connection tracking as well as the NAT subsystems together build the whole framework. IMPORTANT NOTES: System security is a discipline that cannot be achieved by simply installing the iptables package -- the iptables package is NOT a firewall package. Also, misused rulesets can easily disallow you access to remote and local (yes, even localhost) network services. From Debian 3.0r0 APT

3. The iptables utility controls the network packet filtering code in the Linux kernel. If you need to set up firewalls and/or IP masquerading, you should install this package. From Redhat 8.0 RPM