Gnatbox
The GNAT Box System software is a comprehensive firewall system that prevents unauthorized access from the untrusted network, completely hides your internal network, and provides transparent network access to users on the protected hidden network. The system utilizes packet inspection and application firewall techniques combined with a powerful network address translation system. Unlike some firewall systems, the GNAT Box System software provides the user with complete transparent network access to external and private service networks for IP protocols (e.g. TCP, UDP, and ICMP) based applications.
