A Cyber-Physical System Testbed for Security Experimentation

Cyber-Physical Systems (CPSs) can be defined as an integration of various computation, networking and physical processes. CPSs that operate critical functions have many requirements, such as robustness, safety and security, Quality of Service (QoS) and trust. As CPSs typically combine a wide variety of hardware, software, digital and analog technologies, engineering these requirements through analysis, verification and controls is incredibly challenging. With respect to security, the science of protecting CPSs from blended attacks (combining attacks on digital and physical aspects) is yet to be developed. On this front, one much-needed component is a suitable environment in which to pursue lines of experimentation and exploration. In this paper, we introduce a special testbed under development that will allow security researchers to experiment with blended attack/defend scenarios in CPSs. The testbed also constitutes a competitive learning environment in which students can explore and master fundamental concepts, techniques and practices for defending CPSs. Examples and approaches for applying the testbed in CPS security education and research are presented.

Cyber Physical Systems (CPS) are characterized by their ability to integrate\nthe physical and information or cyber worlds. Their deployment in critical\ninfrastructure have demonstrated a potential to transform the world. However,\nharnessing this potential is limited by their critical nature and the far\nreaching effects of cyber attacks on human, infrastructure and the environment.\nAn attraction for cyber concerns in CPS rises from the process of sending\ninformation from sensors to actuators over the wireless communication medium,\nthereby widening the attack surface. Traditionally, CPS security has been\ninvestigated from the perspective of preventing intruders from gaining access\nto the system using cryptography and other access control techniques. Most\nresearch work have therefore focused on the detection of attacks in CPS.\nHowever, in a world of increasing adversaries, it is becoming more difficult to\ntotally prevent CPS from adversarial attacks, hence the need to focus on making\nCPS resilient. Resilient CPS are designed to withstand disruptions and remain\nfunctional despite the operation of adversaries. One of the dominant\nmethodologies explored for building resilient CPS is dependent on machine\nlearning (ML) algorithms. However, rising from recent research in adversarial\nML, we posit that ML algorithms for securing CPS must themselves be resilient.\nThis paper is therefore aimed at comprehensively surveying the interactions\nbetween resilient CPS using ML and resilient ML when applied in CPS. The paper\nconcludes with a number of research trends and promising future research\ndirections. Furthermore, with this paper, readers can have a thorough\nunderstanding of recent advances on ML-based security and securing ML for CPS\nand countermeasures, as well as research trends in this active research area.\n

Security and Privacy Aspect of Cyber Physical Systems

Cyber Physics Systems consists of physical systems and information systems. Modern power systems are increasingly dependent on information systems, experts and scholars are paying more and more attention to cyber attacks on CPS. This paper first introduces the existing research on cyber physical power system. Then this paper reviews the current status of existing cyber attacks. Finally, the modeling method for CPS is summarized such as correlation characteristic matrix, graph theory, complex network theory, finite state machine, mathematical programming and cellular automata method. These methods have vital theoretical and practical significance for the research of cyber physical power system.

An agent-based framework is presented to model and analyze physical and cyber attacks on Cyber Physical Systems (CPS). In the first phase of a two phase procedure in the framework, a CPS is modelled using State Condition Graphs (SCGs) representing the structural relations among the cyber and physical components. In the second phase, SCGs are partitioned into separate groups, referred to as agents, based on their functional dependency. Each agent is associated with a sensor and an actuator set. The actuator set is further divided into two subsets: active actuator and passive subsets that, respectively, directly or indirectly participate in controlling the environment. Interactions among different agents can be created by assigning an aggregate function to each agent with sensor and actuator sets as the domain of the function and status of the environment as its codomain. A case study was conducted on a segment of a 6-stage Secure Water Treatment (SWaT) system to demonstrate the applicability of the framework. The study reveals promising features of the framework to analyze the steady state response of the system following both cyber and physical attacks.

“The Internet has made the world “flat” by transcending space. […] The Internet has transformed how we conduct research, studies, business, services, and entertainment.” [1] Cyber-physical systems (CPS) are engineered systems that are built from, and depend upon, the seamless integration of computational algorithms and physical components. Advances in CPS will enable capability, adaptability, scalability, resiliency, safety, security, and usability that will far exceed the embedded systems of today. CPS technology will transform the way people interact with engineered systems. “CPS have a highly disruptive effect on market structures. They will fundamentally change business models and the competitive field of today […]” [2] Usability is a driving force for the rapid take-up and acceptance of these Cyber-physical systems. [2] In this paper we define CPS and highlight the importance of usability for CPS. Then we describe two different cases and provide different methods how to improve the usability of CPS.

Cyber-physical systems (CPSs) are engineered solutions obtained through the seamless integration of computational algorithms and physical components. Nowadays, they are entitled to drive innovation and competition in different fields such as agriculture, building design and automation, energy, healthcare, transportation and, above all, industrial manufacturing. In fact, CPS technology is going to transform the way people interact with engineered systems — just as the Internet has transformed the way people interact with information. Among CPS technologies, measurement and networking ones play a fundamental role, being enrolled as the natural bridge between the cyber and physical components of a CPS. A number of interconnected sensors and transducers are claimed to give inner and outer, local measurement data that, once processed through suitable algorithms and analytics, have to provide reliable information about the effectiveness of the whole CPS and its interaction with the external world, as well as its health status for maintenance and troubleshooting purposes. So, great attention has to be paid to network models and architectures, to sensor forms and functions, in order to make CPSs properly integrate the continuous and the discrete, compounded by the uncertainty of open environments. The paper aims at opening a preliminary discussion on the role and features of measurement and networking technologies in CPS application fields, with special regard to industrial manufacturing, within a scientific community traditionally close to instrumentation and measurement (IM) issues, in order to stimulate and encourage useful and fruitful cross-fertilization. After some details concerning the general structure of a CPS, its typical architectural model and main features, a special focus is put on CPSs involved in industrial manufacturing along with measurement and networking facets. Some considerations about major measurement challenges that the CPS self-awareness feature poses in maintenance and troubleshooting operations are then drawn. Concluding remarks are finally reported.

In cyber-physical systems (CPSs), embedded computing systems and communication capability are used to streamline and fortify the operation of a physical system. Intelligent critical infrastructure systems are among the most important CPSs and also prime examples of pervasive computing systems, as they exploit computing to provide anytime, anywhere transparent services. While the added intelligence offers the promise of increased utilization, its impact must be assessed, as unrestricted cyber control can actually lower the reliability of existing infrastructure systems. As a practical example, water distribution networks (WDNs) are an emerging CPS domain. Physical components, e.g., valves, pipes, and reservoirs, are coupled with the hardware and software that support intelligent water allocation. An example is depicted in Fig. 1. The primary goal of WDNs is to provide a dependable source of potable water to the public. Information such as demand patterns, water quantity (flow and pressure head), and water quality (contaminants and minerals) is critical in achieving this goal, and beneficial in guiding maintenance efforts and identifying vulnerable areas requiring fortification and/or monitoring. Sensors dispersed in the physical infrastructure collect this information, which is fed to algorithms (often distributed) running on the cyber infrastructure. These algorithms provide decision support to hardware controllers that are used to manage the allocation (quantity) and chemical composition (quality) of the water. As WDNs become larger and more complex, their reliability comes into question. Modeling and simulation can be used to analyze CPS performability, as direct observation of critical infrastructure is often infeasible. Accurate representation of a CPS encompasses three aspects: computing, communication, and the physical infrastructure. Fundamental differences exist between the attributes of cyber and physical components, significantly complicating representation of their behavior with a single comprehensive model or simulation tool. Specialized simulation tools exist for the engineering domains represented in critical infrastructure, including power, water, and transportation. These tools have been created with the objective of accurately reflecting the operation of the physical system, at high spatial and temporal resolution. As is the case with specialized models of physical systems, intelligent control is not reflected in these tools. Despite the existence of simulation tools for cyber aspects such as computing and communication, differences in temporal resolution and 7

This paper presents definitions characterizing the concepts regarding cyber-physical systems and dependability. Cyber-physical systems incorporate computing, communication and storage capabilities with monitoring and/or control of entities in the physical world in a dependably, securely, efficiently and real-time way. The challenges of cyber-physical system research are concerning: real-time system abstractions; robustness, safety and security; QoS composition; and nor least dependability. Dependability is first introduced as a global concept that subsumes the usual attributes of reliability, availability, safety, integrity and maintainability. The paper aims to define research challenges to achieve the dependability in cyber-physical hydropower systems. The significant challenge of the dependability in cyber-physical hydropower systems is evaluation of the system behavior in terms of interdependencies between cyber and physical components of the system.

There is a crucial need to enhance the reliability and resilience of our nation’s critical energy infrastructure. Electric power systems are cyber-physical critical infrastructure with distinct, interacting networks comprising electrical, communications, and interdependency layers. Resilience requires modeling and monitoring all layers for prevention, early detection, and proactive threat assessment. This paper presents the research and design of a novel energy management system (EMS) called Cyber-Physical Resilient Energy Systems (CYPRES) to accomplish this goal. The CYPRES EMS architecture and methods are all cyber-physical to cohesively model and analyze the power system as a cyber-physical system (CPS). Results are illustrated for this proof-of-concept solution utilizing a 2000-bus cyber-physical synthetic electric grid.

Cyberphysical system is the integration of physical space (equipment, devices and people) with computing, communication and control systems (cyberspace). The National Institute of Standards and Terminology (NIST) has defined CFS as cyberphysical systems (CFS), which are designed systems built on the continuous integration of computational algorithms and physical components. Improving the CFS provides greater opportunities for performance, adaptability, scalability, stability, security and usability, far exceeding today's simple embedded systems. CFS technology will transform the interaction of people with the engineering system [1, 2]. Today, cyberphysical systems exist in various fields, such as automotive, aerospace, civil, railway, medical. Large productions seek to increase the availability of the asset, while reducing maintenance costs through cyberphysical systems. With the development of the industry and the use of systems in production, the proposed maintenance is used constantly to avoid failures. CFS maintenance is performed when certain indicators signal that the condition of the system has deteriorated. One way to solve this problem is to provide systems with resistance properties. Such systems are able to recover quickly and continue to function in changing conditions [3-9]. Therefore, the urgent task is to develop approaches that will predict the resilience of cyberphysical systems based on cloud computing. It is necessary to build methods and tools that will monitor the condition of the CFS and predict the timely replacement of their components that may fail. The application of the process of predicting the resilience of cyberphysical systems using cloud-oriented increases the effective reliability and availability of cyberphysical systems in its life cycle by identifying future failures and reducing unscheduled maintenance. The forecasting process involves the assessment of the useful life, and the implementation of a post-forecast decision on maintenance measures in accordance with the rules. The method of predicting the resilience of cloud-oriented cyberphysical systems allows to determine the state of the cyberphysical systems using cloud computing. The mechanism used to reduce the cost of maintenance and detailed planning of maintenance operations, the apparatus of genetic algorithms.

Context: Cyber-physical systems (CPS) seamlessly integrate computational and physical components. Adaptability, realized through feedback loops, is a key requirement to deal with uncertain operating conditions in CPS. Objective: We aim at assessing state-of-art approaches to handle self-adaptation in CPS at the architectural level. Method: We conducted a systematic literature review by searching four major scientific data bases, resulting in 1103 candidate studies and eventually retaining 42 primary studies included for data collection after applying inclusion and exclusion criteria. Results: The primary concerns of adaptation in CPS are performance, flexibility, and reliability. 64% of the studies apply adap- tation at the application layer and 24% at the middleware layer. MAPE (Monitor-Analyze-Plan-Execute) is the dominant adaptation mechanism (60%), followed by agents and self-organization (both 29%). Remarkably, 36% of the studies combine differ- ent mechanisms to realize adaptation; 17% combine MAPE with agents. The dominating application domain is energy (24%). Conclusions: Our findings show that adaptation in CPS is a cross-layer concern, where solutions combine different adaptation mechanisms within and across layers. This raises challenges for future research both in the field of CPS and self-adaptation, including: how to map concerns to layers and adaptation mechanisms, how to coordinate adaptation mechanisms within and across layers, and how to ensure system-wide consistency of adaptation.

Establishment of intrusion detection testbed for CyberManufacturing systems

Cyber-Physical Systems (CPS) involve communication, computation, sensing, and actuating through heterogeneous and widely distributed physical devices and computational components. The close interactions of these systems with the physical world places events as the major building blocks for the realization of CPS. More specifically, the system components and design principles should be revisited with a strictly event-based approach. In this paper, a concept lattice-based event model for CPS is introduced. Under this model, a CPS event is uniformly represented by three components: event type, its internal attributes, and its external attributes. The internal and external attributes together characterize the type, spatiotemporal properties of the event as well as the components that observe it. A set of event composition rules are defined where the CPS event composition is based on a CPS concept lattice. The resulting event model can be used both as an offline analysis tool as well as a run-time implementation model due to its distributed nature. A real-life smart home example is used to illustrate the proposed event model. To this end, a CPS event simulator is implemented to evaluate the developed event model and compare with the existing Java implementation of the smart home application. The comparison result shows that the event model provides several advantages in terms of flexibility, QoS support, and complexity. The proposed event model lay the foundations of event-based system design in CPS.

Naval forces rely heavily on Cyber-Physical Systems (CPS) to conduct operations and achieve mission success. As CPS infrastructure becomes exposed to the contested world through networks, CPS security becomes much more important. In a CPS, the cyber components manage the physical components. ONR proposes that the overall goal for CPS resiliency is to have the physical systems behave properly regardless of fault and disruption. Our approach to CPS resiliency focuses on the physical components. We observed that the inertia of the physical components provides a natural but limited resilience, and is capable of tolerating short-term disruption without affecting the health and safety of the CPS. This and the fact that a CPS has a large difference between physical and cyber time scales, enables a unique approach to CPS resiliency. We present Byzantine Fault Tolerant++ (BFT++), a cyber resilient architecture that engineers the cyber components to be brittle against attack, which consequently forces cyber attacks and related disruptions to be short-lived and within tolerance of the physical system’s inertia.