5.1 Introduction Critical infrastructure (CI) includes any systems and assets that are so vital that their destruction or disruption threatens lives, governments, economies, ecologies, or the social/political structure of nations (Moteff & Parfomak, 2004) (Luiijf & Klaver, 2004). Thus, CI includes, but is not limited to, power grids, water and sewage, hospitals, and transportation systems (Luiijf & Klaver, 2004). To enable monitoring and control of CI systems, industrial control networks are often used (Galloway & Hancke, 2013). Industrial control networks, conceptualized in Figure 5.1, are systems that monitor and control physical devices. Conservatively, eighty percent of US electric power utilities employ industrial control networks for monitoring and control (Fernandez & Fernandez, 2005). Of interest in industrial control networks is preventing unauthorized access to CI systems and overall reliability of the networks. Figure 5.1: Conceptualization of an Industrial Control Network (from (Goverment Accountability Office (GAO), 2008)) Increasingly, commercial network technologies are being used in industrial control networks; this increases internet pathways and cyber security risks. In many ways, extending the Internet EXAMPLE CHAPTER-Contributed chapter of Things (IoT) to include CI components can be seen as logical since IoT enabled devices can be used to monitor all components in a system, e.g. wireless enabled structural health monitoring of bridges (Hu, Wang, & Ji, 2013). However, to be useful, communication networks used for CI need to balance performance, security, reliability, availability, and