Analysis and Design of Secure Sampled-Data Control Subject to Denial-of-Service Attacks

This study addresses the issue of secure control design for cyber-physical systems (CPS) against denial of service (DoS) attacks. We take into account a continuous-time linear system with a convex quadratic performance measure and a sampled linear state feedback control. DoS attacks impose constraints on the CPS, where packets may be jammed between the sensor and controller by a malicious entity, potentially resulting in system instability and performance degradation. We assume that the attacker can perform DoS attacks with a limited time and frequency due to energy restrictions. We devise an efficient procedure using the linear matrix inequality approach to compute an upper bound on the performance degradation brought on by the DoS attack. We also propose a redesign of the controller to minimize this performance degradation. Finally, a simulation example illustrates the computation of the performance degradation under a bounded DoS attack and the design of a secure controller. Simulation results show that the designed controller effectively keeps the feedback loop’s performance and stability under attack

Bibliographical review on cyber attacks from a control oriented perspective

This paper presents a bibliographical review of definitions, classifications and applications concerning cyber attacks in networked control systems (NCSs) and cyber-physical systems (CPSs). This review tackles the topic from a control-oriented perspective, which is complementary to information or communication ones. After motivating the importance of developing new methods for attack detection and secure control, this review presents security objectives, attack modeling, and a characterization of considered attacks and threats presenting the detection mechanisms and remedial actions. In order to show the properties of each attack, as well as to provide some deeper insight into possible defense mechanisms, examples available in the literature are discussed. Finally, open research issues and paths are presented.Peer ReviewedPostprint (author's final draft

Cyber-Attack Detection and Mitigation in Networked Control Systems

Cyber-Physical System (CPS) is the term used to describe the physical systems equipped with computation and communication capabilities. CPSs can be used in different applications e.g. autonomous vehicles, water distribution systems, smart grids, industry 4.0 and Internet of Things (IoT). CPSs have expectation of improving the capability of traditional engineering system but on the other hand, they arise several concerns about their security against cyber-attacks. In the last decade, several cyber-attacks targeting SCADA systems have been reported, see e.g. Maroochy water breach and the Stuxnet worm aimed Iran's nuclear facility. From a control point of view, a CPS can be interpreted as a Networked Control System (NCS) where the risk of cyber-attacks can be modeled as the possibility that malicious agents could compromise the communication channels. In order to bene�t from CPSs, specially in safety critical systems, their vulnerabilities to cyber-attacks must be properly faced. In this thesis two control architectures for CPS are developed. In the first, starting from the analysis of active detection mechanisms available in the literature, we propose a novel architecture capable of detecting a broad class of False Data Injection (FDI) attacks. Such strategy has been contrasted with the well-known watermarking detection mechanism and it is shown that our solution is capable of detecting replay attacks without degrading the closed-loop performance of the system. Moreover, it is shown that compared to detection schemes resorting to auxiliary systems, the proposed strategy is less involved and of easier implementation. In particular, it can be installed on the existing NCS infrastructure without changing communications, controller or state estimator. In the second architecture, we propose another novel architecture capable of detecting and mitigating a broad class of FDI attacks. First, we propose a detection mechanism based on a coding scheme to limit the attacker's disclosure and disruptive resources and prevent the existence of stealthy attacks. Second, we propose an emergency local controller that is activated when an attack is detected or the plant's safety is in danger. It is proved that the proposed architecture always guarantees the safety of the system, regardless of the attack actions and detector performance. Moreover, plant's normal operation recovery is ensured once the attack is terminated

Cyber-Attack Detection and Mitigation in Networked Control Systems

Cyber-Physical System (CPS) is the term used to describe the physical systems equipped with computation and communication capabilities. CPSs can be used in different applications e.g. autonomous vehicles, water distribution systems, smart grids, industry 4.0 and Internet of Things (IoT). CPSs have expectation of improving the capability of traditional engineering system but on the other hand, they arise several concerns about their security against cyber-attacks. In the last decade, several cyber-attacks targeting SCADA systems have been reported, see e.g. Maroochy water breach and the Stuxnet worm aimed Iran's nuclear facility. From a control point of view, a CPS can be interpreted as a Networked Control System (NCS) where the risk of cyber-attacks can be modeled as the possibility that malicious agents could compromise the communication channels. In order to benefit from CPSs, specially in safety critical systems, their vulnerabilities to cyber-attacks must be properly faced. In this thesis two control architectures for CPS are developed. In the first, starting from the analysis of active detection mechanisms available in the literature, we propose a novel architecture capable of detecting a broad class of False Data Injection (FDI) attacks. Such strategy has been contrasted with the well-known watermarking detection mechanism and it is shown that our solution is capable of detecting replay attacks without degrading the closed-loop performance of the system. Moreover, it is shown that compared to detection schemes resorting to auxiliary systems, the proposed strategy is less involved and of easier implementation. In particular, it can be installed on the existing NCS infrastructure without changing communications, controller or state estimator. In the second architecture, we propose another novel architecture capable of detecting and mitigating a broad class of FDI attacks. First, we propose a detection mechanism based on a coding scheme to limit the attacker's disclosure and disruptive resources and prevent the existence of stealthy attacks. Second, we propose an emergency local controller that is activated when an attack is detected or the plant's safety is in danger. It is proved that the proposed architecture always guarantees the safety of the system, regardless of the attack actions and detector performance. Moreover, plant's normal operation recovery is ensured once the attack is terminated

Resilience-oriented control and communication framework for cyber-physical microgrids

Climate change drives the energy supply transition from traditional fossil fuel-based power generation to renewable energy resources. This transition has been widely recognised as one of the most significant developing pathways promoting the decarbonisation process toward a zero-carbon and sustainable society. Rapidly developing renewables gradually dominate energy systems and promote the current energy supply system towards decentralisation and digitisation. The manifestation of decentralisation is at massive dispatchable energy resources, while the digitisation features strong cohesion and coherence between electrical power technologies and information and communication technologies (ICT). Massive dispatchable physical devices and cyber components are interdependent and coupled tightly as a cyber-physical energy supply system, while this cyber-physical energy supply system currently faces an increase of extreme weather (e.g., earthquake, flooding) and cyber-contingencies (e.g., cyberattacks) in the frequency, intensity, and duration. Hence, one major challenge is to find an appropriate cyber-physical solution to accommodate increasing renewables while enhancing power supply resilience. The main focus of this thesis is to blend centralised and decentralised frameworks to propose a collaboratively centralised-and-decentralised resilient control framework for energy systems i.e., networked microgrids (MGs) that can operate optimally in the normal condition while can mitigate simultaneous cyber-physical contingencies in the extreme condition. To achieve this, we investigate the concept of "cyber-physical resilience" including four phases, namely prevention/upgrade, resistance, adaption/mitigation, and recovery. Throughout these stages, we tackle different cyber-physical challenges under the concept of microgrid ranging from a centralised-to-decentralised transitional control framework coping with cyber-physical out of service, a cyber-resilient distributed control methodology for networked MGs, a UAV assisted post-contingency cyber-physical service restoration, to a fast-convergent distributed dynamic state estimation algorithm for a class of interconnected systems.Open Acces

Trust-based fault detection and robust fault-tolerant control of uncertain cyber-physical systems against time-delay injection attacks

Control systems need to be able to operate under uncertainty and especially under attacks. To address such challenges, this paper formulates the solution of robust control for uncertain systems under time-varying and unknown time-delay attacks in cyber-physical systems (CPSs). A novel control method able to deal with thwart time-delay attacks on closed-loop control systems is proposed. Using a descriptor model and an appropriate Lyapunov functional, sufficient conditions for closed-loop stability are derived based on linear matrix inequalities (LMIs). A design procedure is proposed to obtain an optimal state feedback control gain such that the uncertain system can be resistant under an injection time-delay attack with variable delay. Furthermore, various fault detection frameworks are proposed by following the dynamics of the measured data at the system's input and output using statistical analysis such as correlation analysis and K-L (Kullback-Leibler) divergence criteria to detect attack's existence and to prevent possible instability. Finally, an example is provided to evaluate the proposed design method's effectiveness

State of the art of cyber-physical systems security: An automatic control perspective

Cyber-physical systems are integrations of computation, networking, and physical processes. Due to the tight cyber-physical coupling and to the potentially disrupting consequences of failures, security here is one of the primary concerns. Our systematic mapping study sheds light on how security is actually addressed when dealing with cyber-physical systems from an automatic control perspective. The provided map of 138 selected studies is defined empirically and is based on, for instance, application fields, various system components, related algorithms and models, attacks characteristics and defense strategies. It presents a powerful comparison framework for existing and future research on this hot topic, important for both industry and academia

Foundations of Infrastructure CPS

Infrastructures have been around as long as urban centers, supporting a society’s needs for its planning, operation, and safety. As we move deeper into the 21st century, these infrastructures are becoming smart – they monitor themselves, communicate, and most importantly self-govern, which we denote as Infrastructure CPS. Cyber-physical systems are now becoming increasingly prevalent and possibly even mainstream. With the basics of CPS in place, such as stability, robustness, and reliability properties at a systems level, and hybrid, switched, and eventtriggered properties at a network level, we believe that the time is right to go to the next step, Infrastructure CPS, which forms the focus of the proposed tutorial. We discuss three different foundations, (i) Human Empowerment, (ii) Transactive Control, and (iii) Resilience. This will be followed by two examples, one on the nexus between power and communication infrastructure, and the other between natural gas and electricity, both of which have been investigated extensively of late, and are emerging to be apt illustrations of Infrastructure CPS