Krishna Dagli writes to mention a post by Bruce Schneier on his site indicating that the U.S. Navy may be patenting the Firewall. Whether or not it is their intention to do so is unclear. From the patent description: "In a communication system having a plurality of networks, a method of achieving network separation between first and second networks is described. First and second networks with respective first and second degrees of trust are defined, the first degree of trust being higher than the second degree of trust. Communication between the first and second networks is enabled via a network interface system having a protocol stack, the protocol stack implemented by the network interface system in an application layer."