1. A method for constructing a dynamically adaptive network firewall, comprising: establishing a firewall model for the firewall, wherein the firewall model defines nodes, connections between the nodes, and firewall rules applicable to the nodes, to the connections between the nodes, or to a combination thereof, wherein each of the nodes represents simultaneously a source and a destination for data packets, wherein the firewall rules in the firewall model comprise dynamic chains of rules, and wherein the dynamic chains comprise defined places for functional extensions thereto; implementing the firewall on one or more machines connected to network segments where the nodes reside; and dynamically inserting a firewall rule at one of the defined places while the firewall is operating on the one or more machines.