We will cover IoT security engineering in the following chapters, but for now we would like to emphasize how cross-discipline security engineering is in the real world. One struggles to find it covered in academic curricula outside of a few university computer science programs, network engineering, or dedicated security programs such as SANS. Most security practitioners have strong computer science and networking skills but are less versed in the physical and safety engineering disciplines covered by core engineering curricula. So, the cyber-physical aspects of the IoT face a safety versus security clash of cultures and conundrums:

Because the IoT is concerned with connecting physically engineered and manufactured objects—and thus may be a CPS—this conundrum more than any other comes into play. The IoT device engineer may be well versed in safety issues, but not fully understand the security implications of design decisions. Likewise, skilled security engineers may not understand the physical engineering nuances of a thing to ascertain and characterize its physical-world interactions (in its intended environment) and fix them. In other words, core engineering disciplines typically focus on functional design, creating things to do what we want them to do. Security engineering shifts the view to consider what the thing can do and how one might misuse it in ways the original designer never considered. Malicious hackers depend on this. The refrigeration system engineer never had to consider a cryptographic access control scheme in what was historically a basic thermodynamic system design. Now, designers of connected refrigerators do, because malicious hackers will look for unauthenticated data originating from the refrigerator or attempt to exploit it and pivot to additional nodes in a home network.

Security engineering is maturing as a cross-discipline, fortunately. One can argue that it is more efficient to enlighten a broad range of engineering professionals in baseline security principles than it is to train existing security engineers in all physical engineering subjects. Improving IoT security requires that security engineering tenets and principles be learned and promulgated by the core engineering disciplines in their respective industries. If not, industries will never succeed in responding well to emergent threats. Such a response requires appropriating the right security mitigations at the right time when they are the least expensive to implement (that is, the original design as well as its flexibility and accommodation of future-proofing principles). For example, a thermodynamics process and control engineer designing a power-plant will have tremendous knowledge concerning the physical processes of the control system, safety redundancies, and so on. If she understands security engineering principles, she will be in a much better position to dictate additional sensors, redundant state estimation logic, or redundant actuators based on certain exposures to other networks. In addition, she will be in a much better position to ascertain the sensitivity of certain state variables and timing information that network, host, application, sensor, and actuator security controls should help protect. She can better characterize the cyber-attack and control system interactions that might cause gas pressure and temperature tolerances to be exceeded with a resultant explosion. The traditional network cybersecurity engineer will not have the physical engineering basis on which to orchestrate these design decisions.

Before characterizing today's IoT devices and enterprises, it should be clear how cross-cutting the IoT is across industries. Medical device and biomedical companies, automotive and aircraft manufacturers, the energy industry, even video game makers and broad consumer markets are involved in the IoT. These industries, historically isolated from each other, must learn to collaborate when it comes to securing their devices and infrastructure. Unfortunately, there are some in these industries who believe that most security mitigations need to be developed and deployed uniquely in each industry. This isolated, turf-protecting approach is ill-advised and short-sighted. It has the potential of stifling valuable cross-industry security collaboration, learning, and development of common countermeasures.

IoT security is an equal-opportunity threat environment; the same threats against one industry exist against the others. An attack and compromise of one device today may represent a threat to devices in almost all other industries. A smart light bulb installed in a hospital may be compromised and used to perform various privacy attacks on medical devices. In other words, the cross-industry relationship may be due to intersections in the supply chain or the fact that one industry's IoT implementations were added to another industry's systems. Real-time intelligence as well as lessons learned from attacks against industrial control systems should be leveraged by all industries and tailored to suit. Threat intelligence, defined well by Gartner, is: evidence-based knowledge, including context, mechanisms, indicators, implications and actionable advice, about an existing or emerging menace or hazard to assets that can be used to inform decisions regarding the subject's response to that menace or hazard (http://www.gartner.com/document/2487216).

The discovery, analysis, understanding and sharing of how real-world threats are compromising ever-present vulnerabilities needs to be improved for the IoT. No single industry, government organization, standards body or other entity can assume to be the dominant control of threat intelligence and information sharing. Security is an ecosystem.

As a government standards body, NIST is well aware of this problem. NIST's recently formed CPS Public Working Group represents a cross-industry collaboration of security professionals working to build a framework approach to solving many cyber-physical IoT challenges facing different industries. It is accomplishing this in meta-form through its draft Framework for Cyber-Physical Systems. This framework provides a useful reference frame from which to describe CPS along with their security and physical properties. Industries will be able to leverage the framework to improve and communicate CPS designs and provide a basis on which to develop system-specific security standards. This book will address CPS security in more detail in terms of common patterns that span many industries.

Like the thermodynamics example we provided above, cyber-physical and many IoT systems frequently invoke an intersection of safety and security engineering, two disciplines that have developed on very different evolutionary paths but which possess partially overlapping goals. We will delve more into safety aspects of IoT security engineering later in this volume, but for now we point out an elegantly expressed distinction between safety and security provided by noted academic Dr. Barry Boehm, Axelrod, W. C., Engineering Safe and Secure Software Systems, p.61, Massachussetts, Artech House, 2013. He poignantly but beautifully expressed the relationship as follows:

Thus it is clear that the IoT and IoT security are much more complex than traditional networks, hosts and cybersecurity. Safety-conscious industries such as aircraft manufacturers, regulators, and researchers have evolved highly effective safety engineering approaches and standards because aircraft can harm the world, and the people in it. The aircraft industry today, like the automotive industry, is now playing catch-up with regard to security due to the accelerating growth of network connectivity to their vehicles.