Biblio

An application of two Cyber-Physical System (CPS) security countermeasures - Intelligent Checker (IC) and Cross-correlator - for enhancing CPS safety and achieving required CPS safety integrity level is presented. ICs are smart sensors aimed at detecting attacks in CPS and alerting the human operators. Cross-correlator is an anomaly detection technique for detecting deception attacks. We show how ICs could be implemented at three different CPS safety protection layers to maintain CPS in a safe state. In addition, we combine ICs with the cross-correlator technique to assure high probability of failure detection. Performance simulations show that a combination of these two security countermeasures is effective in detecting and mitigating CPS failures, including catastrophic failures.
 

The newly emerging cyber-physical systems (CPS) discover events from multiple, distributed sources with multiple levels of detail and heterogeneous data format, which may not be compare and integrate, and turn to hardly combined determination for action. While existing efforts have mainly focused on investigating a uniform CPS event representation with spatio-temporal attributes, in this paper we propose a new event model with two-layer structure, Basic Event Model (BEM) and Extended Information Set (EIS). A BEM could be extended with EIS by semantic adaptor for spatio-temporal and other attribution enhancement. In particular, we define the event process functions, like event attribution extraction and composition determination, for CPS action trigger exploit the Complex Event Process (CEP) engine Esper. Examples show that such event model provides several advantages in terms of extensibility, flexibility and heterogeneous support, and lay the foundations of event-based system design in CPS.
 

Establishing trust relationships between network participants by having them prove their operating system's integrity via a Trusted Platform Module (TPM) provides interesting approaches for securing local networks at a higher level. In the introduced approach on OSI layer 2, attacks carried out by already authenticated and participating nodes (insider threats) can be detected and prevented. Forbidden activities and manipulations in hard- and software, such as executing unknown binaries, loading additional kernel modules or even inserting unauthorized USB devices, are detected and result in an autonomous reaction of each network participant. The provided trust establishment and authentication protocol operates independently from upper protocol layers and is optimized for resource constrained machines. Well known concepts of backbone architectures can maintain the chain of trust between different kinds of network types. Each endpoint, forwarding and processing unit monitors the internal network independently and reports misbehaviours autonomously to a central instance in or outside of the trusted network.

Smart grids utilize computation and communication to improve the efficacy and dependability of power generation, transmission, and distribution. As such, they are among the most critical and complex cyber-physical systems. The success of smart grids in achieving their stated goals is yet to be rigorously proven. In this paper, our focus is on improvements (or lack thereof) in reliability. We discuss vulnerabilities in the smart grid and their potential impact on its reliability, both generally and for the specific example of the IEEE-14 bus system. We conclude the paper by presenting a preliminary Markov imbedded systems model for reliability of smart grids and describe how it can be evolved to capture the vulnerabilities discussed.
 

Modern power systems heavily rely on the associated cyber network, and cyber attacks against the control network may cause undesired consequences such as load shedding, equipment damage, and so forth. The behaviors of the attackers can be random, thus it is crucial to develop novel methods to evaluate the adequacy of the power system under probabilistic cyber attacks. In this study, the external and internal cyber structures of the substation are introduced, and possible attack paths against the breakers are analyzed. The attack resources and vulnerability factors of the cyber network are discussed considering their impacts on the success probability of a cyber attack. A procedure integrating the reliability of physical components and the impact of cyber attacks against breakers are proposed considering the behaviors of the physical devices and attackers. Simulations are conducted based on the IEEE RTS79 system. The impact of the attack resources and attack attempt numbers are analyzed for attackers from different threats groups. It is concluded that implementing effective cyber security measures is crucial to the cyber-physical power grids.

Contingency analysis is a critical activity in the context of the power infrastructure because it provides a guide for resiliency and enables the grid to continue operating even in the case of failure. In this paper, we augment this concept by introducing SOCCA, a cyber-physical security evaluation technique to plan not only for accidental contingencies but also for malicious compromises. SOCCA presents a new unified formalism to model the cyber-physical system including interconnections among cyber and physical components. The cyber-physical contingency ranking technique employed by SOCCA assesses the potential impacts of events. Contingencies are ranked according to their impact as well as attack complexity. The results are valuable in both cyber and physical domains. From a physical perspective, SOCCA scores power system contingencies based on cyber network configuration, whereas from a cyber perspective, control network vulnerabilities are ranked according to the underlying power system topology.

Multiple Security Domains Nondeducibility, MSDND, yields results even when the attack hides important information from electronic monitors and human operators. Because MSDND is based upon modal frames, it is able to analyze the event system as it progresses rather than relying on traces of the system. Not only does it provide results as the system evolves, MSDND can point out attacks designed to be missed in other security models. This work examines information flow disruption attacks such as Stuxnet and formally explains the role that implicit trust in the cyber security of a cyber physical system (CPS) plays in the success of the attack. The fact that the attack hides behind MSDND can be used to help secure the system by modifications to break MSDND and leave the attack nowhere to hide. Modal operators are defined to allow the manipulation of belief and trust states within the model. We show how the attack hides and uses the operator's trust to remain undetected. In fact, trust in the CPS is key to the success of the attack.

Networked control systems consist of distributed sensors and actuators that communicate via a wireless network. The use of an open wireless medium and unattended deployment leaves these systems vulnerable to intelligent adversaries whose goal is to disrupt the system performance. In this paper, we study the wormhole attack on a networked control system, in which an adversary establishes a link between two geographically distant regions of the network by using either high-gain antennas, as in the out-of-band wormhole, or colluding network nodes as in the in-band wormhole. Wormholes allow the adversary to violate the timing constraints of real-time control systems by first creating low-latency links, which attract network traffic, and then delaying or dropping packets. Since the wormhole attack reroutes and replays valid messages, it cannot be detected using cryptographic mechanisms alone. We study the impact of the wormhole attack on the network flows and delays and introduce a passivity-based control-theoretic framework for modeling and mitigating the wormhole attack. We develop this framework for both the in-band and out-of-band wormhole attacks as well as complex, hereto-unreported wormhole attacks consisting of arbitrary combinations of in-and out-of band wormholes. By integrating existing mitigation strategies into our framework, we analyze the throughput, delay, and stability properties of the overall system. Through simulation study, we show that, by selectively dropping control packets, the wormhole attack can cause disturbances in the physical plant of a networked control system, and demonstrate that appropriate selection of detection parameters mitigates the disturbances due to the wormhole while satisfying the delay constraints of the physical system.

Networked control systems consist of distributed sensors and actuators that communicate via a wireless network. The use of an open wireless medium and unattended deployment leaves these systems vulnerable to intelligent adversaries whose goal is to disrupt the system performance. In this paper, we study the wormhole attack on a networked control system, in which an adversary establishes a link between two geographically distant regions of the network by using either high-gain antennas, as in the out-of-band wormhole, or colluding network nodes as in the in-band wormhole. Wormholes allow the adversary to violate the timing constraints of real-time control systems by first creating low-latency links, which attract network traffic, and then delaying or dropping packets. Since the wormhole attack reroutes and replays valid messages, it cannot be detected using cryptographic mechanisms alone. We study the impact of the wormhole attack on the network flows and delays and introduce a passivity-based control-theoretic framework for modeling and mitigating the wormhole attack. We develop this framework for both the in-band and out-of-band wormhole attacks as well as complex, hereto-unreported wormhole attacks consisting of arbitrary combinations of in-and out-of band wormholes. By integrating existing mitigation strategies into our framework, we analyze the throughput, delay, and stability properties of the overall system. Through simulation study, we show that, by selectively dropping control packets, the wormhole attack can cause disturbances in the physical plant of a networked control system, and demonstrate that appropriate selection of detection parameters mitigates the disturbances due to the wormhole while satisfying the delay constraints of the physical system.