a private overlay network is introduced into an existing core network infrastructure to control information flow between private secure environments . such a scheme can be used to connect a factory automation network linking operations devices to a corporate network linking various business units , with enhanced network security . such a connection can be facilitated by introducing into the existing infrastructure a set of industrial security appliances that work together to create an encrypted tunnel between the two networks . the set of isas can be scalable to overlay differently sized core networks , to create the private overlay network . connections to the private overlay network can be managed by the isas in a distributed fashion , implementing a peer - to - peer dynamic mesh policy . the industrial security system disclosed may be particularly advantageous in environments such as public utility systems , medical facilities , and energy delivery systems .