Conclusion
Implementation of a free firewall based on an IP filter

Available by default in many operating systems or as an easy-to-install module, IP Filter offers a comprehensive, high-performance firewall software solution that can be used to protect both a server and a perimeter. Unlike other free firewall solutions, IP Filter's syntax is clear, intuitive and therefore very easy to use. In addition, the software offers commands for address and port translation, as well as access control and tracing functions. Finally, for those less familiar with Unix text editors, there are also free man-machine interfaces for easy parameterization of IP Filter.