A new license for the FL mGuard security devices can protect OPC Classic applications. Users of mGuard firmware version 8.1 and beyond now can upgrade to the OPC inspector license. The OPC inspector firmware looks into the transmitted data packets, analyzing and modifying them as necessary. The OPC inspector dynamically creates firewall rules matching the ports and directions used by OPC traffic. It identifies and blocks all non-OPC traffic. It also permits the use of network address translation (NAT) procedures, such as masquerading or 1:1 NAT routing.