IP Filter is a TCP/IP packet filter suitable for use in a firewall environment. To use, it can either be run as a loadable kernel module (recommended) or incorporated into your UNIX kernel. Scripts are provided to install and patch system files as required.
You can download it from the following link: https://packetstormsecurity.com/files/download/17832/ip_fil3.4.1.tar.gz
Source: https://packetstormsecurity.com/files/17832/ip_fil3.4.1.tar.gz.html