The Industrial Internet of Things (IIoT) promises transformational opportunities. Yet the open, standards-based internet technologies that enable the IIoT and economic innovation also present an array of complex challenges to critical infrastructure providers. Technology is being embedded into existing Industrial and Automation Control Systems (IACS) deployments and the IIoT is being used to monitor and optimize IACS processes, with more and more network connections being made to enable digitization strategies. While the electronics of brownfield critical infrastructure