ipchains
ipchains is an older packet filtering - software . It was developed in 1999 by Rusty Russell on the basis of Ipfwadm and was built into the Linux kernel in the 2.2 version series, in version 2.4 it was replaced by the successor Netfilter / Iptables .
IPChains is similar to the Cisco Access Control Lists, it controls which packets can enter and exit the system. Although it primarily as a firewall is used, you can also use it to a Linux - operating system to further harden .