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2019-12-16
Lopes, José, Robb, David A., Ahmad, Muneeb, Liu, Xingkun, Lohan, Katrin, Hastie, Helen.  2019.  Towards a Conversational Agent for Remote Robot-Human Teaming. 2019 14th ACM/IEEE International Conference on Human-Robot Interaction (HRI). :548–549.

There are many challenges when it comes to deploying robots remotely including lack of operator situation awareness and decreased trust. Here, we present a conversational agent embodied in a Furhat robot that can help with the deployment of such remote robots by facilitating teaming with varying levels of operator control.

2019-12-02
Elfar, Mahmoud, Zhu, Haibei, Cummings, M. L., Pajic, Miroslav.  2019.  Security-Aware Synthesis of Human-UAV Protocols. 2019 International Conference on Robotics and Automation (ICRA). :8011–8017.
In this work, we synthesize collaboration protocols for human-unmanned aerial vehicle (H-UAV) command and control systems, where the human operator aids in securing the UAV by intermittently performing geolocation tasks to confirm its reported location. We first present a stochastic game-based model for the system that accounts for both the operator and an adversary capable of launching stealthy false-data injection attacks, causing the UAV to deviate from its path. We also describe a synthesis challenge due to the UAV's hidden-information constraint. Next, we perform human experiments using a developed RESCHU-SA testbed to recognize the geolocation strategies that operators adopt. Furthermore, we deploy machine learning techniques on the collected experimental data to predict the correctness of a geolocation task at a given location based on its geographical features. By representing the model as a delayed-action game and formalizing the system objectives, we utilize off-the-shelf model checkers to synthesize protocols for the human-UAV coalition that satisfy these objectives. Finally, we demonstrate the usefulness of the H-UAV protocol synthesis through a case study where the protocols are experimentally analyzed and further evaluated by human operators.
2019-09-23
Babu, S., Markose, S..  2018.  IoT Enabled Robots with QR Code Based Localization. 2018 International Conference on Emerging Trends and Innovations In Engineering And Technological Research (ICETIETR). :1–5.

Robots are sophisticated form of IoT devices as they are smart devices that scrutinize sensor data from multiple sources and observe events to decide the best procedural actions to supervise and manoeuvre objects in the physical world. In this paper, localization of the robot is addressed by QR code Detection and path optimization is accomplished by Dijkstras algorithm. The robot can navigate automatically in its environment with sensors and shortest path is computed whenever heading measurements are updated with QR code landmark recognition. The proposed approach highly reduces computational burden and deployment complexity as it reflects the use of artificial intelligence to self-correct its course when required. An Encrypted communication channel is established over wireless local area network using SSHv2 protocol to transfer or receive sensor data(or commands) making it an IoT enabled Robot.

2019-08-05
Gerard, B., Rebaï, S. B., Voos, H., Darouach, M..  2018.  Cyber Security and Vulnerability Analysis of Networked Control System Subject to False-Data Injection. 2018 Annual American Control Conference (ACC). :992-997.

In the present paper, the problem of networked control system (NCS) cyber security is considered. The geometric approach is used to evaluate the security and vulnerability level of the controlled system. The proposed results are about the so-called false data injection attacks and show how imperfectly known disturbances can be used to perform undetectable, or at least stealthy, attacks that can make the NCS vulnerable to attacks from malicious outsiders. A numerical example is given to illustrate the approach.

2019-07-01
Perez, R. Lopez, Adamsky, F., Soua, R., Engel, T..  2018.  Machine Learning for Reliable Network Attack Detection in SCADA Systems. 2018 17th IEEE International Conference On Trust, Security And Privacy In Computing And Communications/ 12th IEEE International Conference On Big Data Science And Engineering (TrustCom/BigDataSE). :633–638.

Critical Infrastructures (CIs) use Supervisory Control And Data Acquisition (SCADA) systems for remote control and monitoring. Sophisticated security measures are needed to address malicious intrusions, which are steadily increasing in number and variety due to the massive spread of connectivity and standardisation of open SCADA protocols. Traditional Intrusion Detection Systems (IDSs) cannot detect attacks that are not already present in their databases. Therefore, in this paper, we assess Machine Learning (ML) for intrusion detection in SCADA systems using a real data set collected from a gas pipeline system and provided by the Mississippi State University (MSU). The contribution of this paper is two-fold: 1) The evaluation of four techniques for missing data estimation and two techniques for data normalization, 2) The performances of Support Vector Machine (SVM), and Random Forest (RF) are assessed in terms of accuracy, precision, recall and F1score for intrusion detection. Two cases are differentiated: binary and categorical classifications. Our experiments reveal that RF detect intrusions effectively, with an F1score of respectively \textbackslashtextgreater 99%.

2019-06-10
Sokolov, A. N., Pyatnitsky, I. A., Alabugin, S. K..  2018.  Research of Classical Machine Learning Methods and Deep Learning Models Effectiveness in Detecting Anomalies of Industrial Control System. 2018 Global Smart Industry Conference (GloSIC). :1-6.

Modern industrial control systems (ICS) act as victims of cyber attacks more often in last years. These attacks are hard to detect and their consequences can be catastrophic. Cyber attacks can cause anomalies in the work of the ICS and its technological equipment. The presence of mutual interference and noises in this equipment significantly complicates anomaly detection. Moreover, the traditional means of protection, which used in corporate solutions, require updating with each change in the structure of the industrial process. An approach based on the machine learning for anomaly detection was used to overcome these problems. It complements traditional methods and allows one to detect signal correlations and use them for anomaly detection. Additional Tennessee Eastman Process Simulation Data for Anomaly Detection Evaluation dataset was analyzed as example of industrial process. In the course of the research, correlations between the signals of the sensors were detected and preliminary data processing was carried out. Algorithms from the most common techniques of machine learning (decision trees, linear algorithms, support vector machines) and deep learning models (neural networks) were investigated for industrial process anomaly detection task. It's shown that linear algorithms are least demanding on computational resources, but they don't achieve an acceptable result and allow a significant number of errors. Decision tree-based algorithms provided an acceptable accuracy, but the amount of RAM, required for their operations, relates polynomially with the training sample volume. The deep neural networks provided the greatest accuracy, but they require considerable computing power for internal calculations.

2019-05-09
Sokolov, A. N., Barinov, A. E., Antyasov, I. S., Skurlaev, S. V., Ufimtcev, M. S., Luzhnov, V. S..  2018.  Hardware-Based Memory Acquisition Procedure for Digital Investigations of Security Incidents in Industrial Control Systems. 2018 Global Smart Industry Conference (GloSIC). :1-7.

The safety of industrial control systems (ICS) depends not only on comprehensive solutions for protecting information, but also on the timing and closure of vulnerabilities in the software of the ICS. The investigation of security incidents in the ICS is often greatly complicated by the fact that malicious software functions only within the computer's volatile memory. Obtaining the contents of the volatile memory of an attacked computer is difficult to perform with a guaranteed reliability, since the data collection procedure must be based on a reliable code (the operating system or applications running in its environment). The paper proposes a new instrumental method for obtaining the contents of volatile memory, general rules for implementing the means of collecting information stored in memory. Unlike software methods, the proposed method has two advantages: firstly, there is no problem in terms of reading the parts of memory, blocked by the operating system, and secondly, the resulting contents are not compromised by such malicious software. The proposed method is relevant for investigating security incidents of ICS and can be used in continuous monitoring systems for the security of ICS.

Hata, K., Sasaki, T., Mochizuki, A., Sawada, K., Shin, S., Hosokawa, S..  2018.  Collaborative Model-Based Fallback Control for Secured Networked Control Systems. IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society. :5963-5970.

The authors have proposed the Fallback Control System (FCS) as a countermeasure after cyber-attacks happen in Industrial Control Systems (ICSs). For increased robustness against cyber-attacks, introducing multiple countermeasures is desirable. Then, an appropriate collaboration is essential. This paper introduces two FCSs in ICS: field network signal is driven FCS and analog signal driven FCS. This paper also implements a collaborative FCS by a collaboration function of the two FCSs. The collaboration function is that the analog signal driven FCS estimates the state of the other FCS. The collaborative FCS decides the countermeasure based on the result of the estimation after cyber-attacks happen. Finally, we show practical experiment results to analyze the effectiveness of the proposed method.

2019-03-06
Kawanishi, Y., Nishihara, H., Souma, D., Yoshida, H., Hata, Y..  2018.  A Study on Quantitative Risk Assessment Methods in Security Design for Industrial Control Systems. 2018 IEEE 16th Intl Conf on Dependable, Autonomic and Secure Computing, 16th Intl Conf on Pervasive Intelligence and Computing, 4th Intl Conf on Big Data Intelligence and Computing and Cyber Science and Technology Congress(DASC/PiCom/DataCom/CyberSciTech). :62-69.

In recent years, there has been progress in applying information technology to industrial control systems (ICS), which is expected to make the development cost of control devices and systems lower. On the other hand, the security threats are becoming important problems. In 2017, a command injection issue on a data logger was reported. In this paper, we focus on the risk assessment in security design for data loggers used in industrial control systems. Our aim is to provide a risk assessment method optimized for control devices and systems in such a way that one can prioritize threats more preciously, that would lead work resource (time and budget) can be assigned for more important threats than others. We discuss problems with application of the automotive-security guideline of JASO TP15002 to ICS risk assessment. Consequently, we propose a three-phase risk assessment method with a novel Risk Scoring Systems (RSS) for quantitative risk assessment, RSS-CWSS. The idea behind this method is to apply CWSS scoring systems to RSS by fixing values for some of CWSS metrics, considering what the designers can evaluate during the concept phase. Our case study with ICS employing a data logger clarifies that RSS-CWSS can offer an interesting property that it has better risk-score dispersion than the TP15002-specified RSS.

2019-02-14
Zhang, S., Wolthusen, S. D..  2018.  Efficient Control Recovery for Resilient Control Systems. 2018 IEEE 15th International Conference on Networking, Sensing and Control (ICNSC). :1-6.

Resilient control systems should efficiently restore control into physical systems not only after the sabotage of themselves, but also after breaking physical systems. To enhance resilience of control systems, given an originally minimal-input controlled linear-time invariant(LTI) physical system, we address the problem of efficient control recovery into it after removing a known system vertex by finding the minimum number of inputs. According to the minimum input theorem, given a digraph embedded into LTI model and involving a precomputed maximum matching, this problem is modeled into recovering controllability of it after removing a known network vertex. Then, we recover controllability of the residual network by efficiently finding a maximum matching rather than recomputation. As a result, except for precomputing a maximum matching and the following removed vertex, the worst-case execution time of control recovery into the residual LTI physical system is linear.

2019-02-08
Zou, Z., Wang, D., Yang, H., Hou, Y., Yang, Y., Xu, W..  2018.  Research on Risk Assessment Technology of Industrial Control System Based on Attack Graph. 2018 IEEE 3rd Advanced Information Technology, Electronic and Automation Control Conference (IAEAC). :2420-2423.

In order to evaluate the network security risks and implement effective defenses in industrial control system, a risk assessment method for industrial control systems based on attack graphs is proposed. Use the concept of network security elements to translate network attacks into network state migration problems and build an industrial control network attack graph model. In view of the current subjective evaluation of expert experience, the atomic attack probability assignment method and the CVSS evaluation system were introduced to evaluate the security status of the industrial control system. Finally, taking the centralized control system of the thermal power plant as the experimental background, the case analysis is performed. The experimental results show that the method can comprehensively analyze the potential safety hazards in the industrial control system and provide basis for the safety management personnel to take effective defense measures.

Lee, D. ', La, W. Gyu, Kim, H..  2018.  Drone Detection and Identification System Using Artificial Intelligence. 2018 International Conference on Information and Communication Technology Convergence (ICTC). :1131-1133.

As drone attracts much interest, the drone industry has opened their market to ordinary people, making drones to be used in daily lives. However, as it got easier for drone to be used by more people, safety and security issues have raised as accidents are much more likely to happen: colliding into people by losing control or invading secured properties. For safety purposes, it is essential for observers and drone to be aware of an approaching drone. In this paper, we introduce a comprehensive drone detection system based on machine learning. This system is designed to be operable on drones with camera. Based on the camera images, the system deduces location on image and vendor model of drone based on machine classification. The system is actually built with OpenCV library. We collected drone imagery and information for learning process. The system's output shows about 89 percent accuracy.

2019-01-16
Schneider, T., Schmidt, H..  2018.  NETSIM: A Realtime Virtual Ocean Hardware-in-the-loop Acoustic Modem Network Simulator. 2018 Fourth Underwater Communications and Networking Conference (UComms). :1–5.
This paper presents netsim, a combined software/hardware system for performing realtime realistic operation of autonomous underwater vehicles (AUVs) with acoustic modem telemetry in a virtual ocean environment. The design of the system is flexible to the choice of physical link hardware, allowing for the system to be tested against existing and new modems. Additionally, the virtual ocean channel simulator is designed to perform in real time by coupling less frequent asynchronous queries to high-fidelity models of the ocean environment and acoustic propagation with frequent pertubation-based updates for the exact position of the simulated AUVs. The results demonstrate the performance of this system using the WHOI Micro-Modem 2 hardware in the virtual ocean environment of the Arctic Beaufort Sea around 73 degrees latitude. The acoustic environment in this area has changed dramatically in recent years due to the changing climate.
Horton, M., Samanta, B., Reid, C., Chen, L., Kadlec, C..  2018.  Development of a Secure, Heterogeneous Cloud Robotics Infrastructure: Implementing a Mesh VPN and Robotic File System Security Practices. SoutheastCon 2018. :1–8.

Robotics and the Internet of Things (IoT) are enveloping our society at an exponential rate due to lessening costs and better availability of hardware and software. Additionally, Cloud Robotics and Robot Operating System (ROS) can offset onboard processing power. However, strong and fundamental security practices have not been applied to fully protect these systems., partially negating the benefits of IoT. Researchers are therefore tasked with finding ways of securing communications and systems. Since security and convenience are oftentimes at odds, securing many heterogeneous components without compromising performance can be daunting. Protecting systems from attacks and ensuring that connections and instructions are from approved devices, all while maintaining the performance is imperative. This paper focuses on the development of security best practices and a mesh framework with an open-source, multipoint-to-multipoint virtual private network (VPN) that can tie Linux, Windows, IOS., and Android devices into one secure fabric, with heterogeneous mobile robotic platforms running ROSPY in a secure cloud robotics infrastructure.

2018-11-14
Shao, Y., Liu, B., Li, G., Yan, R..  2017.  A Fault Diagnosis Expert System for Flight Control Software Based on SFMEA and SFTA. 2017 IEEE International Conference on Software Quality, Reliability and Security Companion (QRS-C). :626–627.
Many accidents occurred frequently in aerospace applications, traditional software reliability analysis methods are not enough for modern flight control software. Developing a comprehensive, effective and intelligent method for software fault diagnosis is urgent for airborne software engineering. Under this background, we constructed a fault diagnosis expert system for flight control software which combines software failure mode and effect analysis with software fault tree analysis. To simplify the analysis, the software fault knowledge of four modules is acquired by reliability analysis methods. Then by taking full advantage of the CLIPS shell, knowledge representation and inference engine can be realized smoothly. Finally, we integrated CLIPS into VC++ to achieve visualization, fault diagnosis and inference for flight control software can be performed in the human-computer interaction interface. The results illustrate that the system is able to diagnose software fault, analysis the reasons and present some reasonable solutions like a human expert.
2018-08-23
Pandey, S. B., Rawat, M. D., Rathod, H. B., Chauhan, J. M..  2017.  Security throwbot. 2017 International Conference on Inventive Systems and Control (ICISC). :1–6.

We all are very much aware of IoT that is Internet of Things which is emerging technology in today's world. The new and advanced field of technology and inventions make use of IoT for better facility. The Internet of Things (IoT) is a system of interrelated computing devices, mechanical and digital machines, objects, animals or people that are provided with unique identifiers and the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. Our project is based on IoT and other supporting techniques which can bring out required output. Security issues are everywhere now-a-days which we are trying to deal with by our project. Our security throwbot (a throwable device) will be tossed into a room after activating it and it will capture 360 degree panaromic video from a single IP camera, by using two end connectivity that is, robot end and another is user end, will bring more features to this project. Shape of the robot will be shperical so that problem of retrieving back can be solved. Easy to use and cheap to buy is one of our goal which will be helpful to police and soldiers who get stuck in situations where they have to question oneself before entering to dangerous condition/room. Our project will help them to handle and verify any area before entering by just throwing this robot and getting the sufficient results.

2018-07-18
Feng, C., Li, T., Chana, D..  2017.  Multi-level Anomaly Detection in Industrial Control Systems via Package Signatures and LSTM Networks. 2017 47th Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN). :261–272.

We outline an anomaly detection method for industrial control systems (ICS) that combines the analysis of network package contents that are transacted between ICS nodes and their time-series structure. Specifically, we take advantage of the predictable and regular nature of communication patterns that exist between so-called field devices in ICS networks. By observing a system for a period of time without the presence of anomalies we develop a base-line signature database for general packages. A Bloom filter is used to store the signature database which is then used for package content level anomaly detection. Furthermore, we approach time-series anomaly detection by proposing a stacked Long Short Term Memory (LSTM) network-based softmax classifier which learns to predict the most likely package signatures that are likely to occur given previously seen package traffic. Finally, by the inspection of a real dataset created from a gas pipeline SCADA system, we show that an anomaly detection scheme combining both approaches can achieve higher performance compared to various current state-of-the-art techniques.

2018-06-11
Yang, J., Zhou, C., Zhao, Y..  2017.  A security protection approach based on software defined network for inter-area communication in industrial control systems. 12th International Conference on System Safety and Cyber-Security 2017 (SCSS). :1–6.

Currently, security protection in Industrial Control Systems has become a hot topic, and a great number of defense techniques have sprung up. As one of the most effective approaches, area isolation has the exceptional advantages and is widely used to prevent attacks or hazards propagating. However, most existing methods for inter-area communication protection present some limitations, i.e., excessively depending on the analyzing rules, affecting original communication. Additionally, the network architecture and data flow direction can hardly be adjusted after being deployed. To address these problems, a dynamical and customized communication protection technology is proposed in this paper. In detail, a security inter-area communication architecture based on Software Defined Network is designed firstly, where devices or subsystems can be dynamically added into or removed from the communication link. And then, a security inspection method based on information entropy is presented for deep network behaviors analysis. According to the security analysis results, the communications in the network can be adjusted in time. Finally, simulations are constructed, and the results indicate that the proposed approach is sensitive and effective for cyber-attacks detection.

2018-06-07
Obster, M., Kowalewski, S..  2017.  A live static code analysis architecture for PLC software. 2017 22nd IEEE International Conference on Emerging Technologies and Factory Automation (ETFA). :1–4.

Static code analysis is a convenient technique to support the development of software. Without prior test setup, information about a later runtime behavior can be inferred and errors in the code can be found before using a regular compiler. Solutions to apply static code analysis to PLC software following the IEC 61131-3 already exist, but using these separate tools usually creates a gap in the development process. In this paper we introduce an architecture to use static analysis directly in a development environment and give instant feedback to the developer while he is still editing the PLC software.

2018-03-19
Back, J., Kim, J., Lee, C., Park, G., Shim, H..  2017.  Enhancement of Security against Zero Dynamics Attack via Generalized Hold. 2017 IEEE 56th Annual Conference on Decision and Control (CDC). :1350–1355.

Zero dynamics attack is lethal to cyber-physical systems in the sense that it is stealthy and there is no way to detect it. Fortunately, if the given continuous-time physical system is of minimum phase, the effect of the attack is negligible even if it is not detected. However, the situation becomes unfavorable again if one uses digital control by sampling the sensor measurement and using the zero-order-hold for actuation because of the `sampling zeros.' When the continuous-time system has relative degree greater than two and the sampling period is small, the sampled-data system must have unstable zeros (even if the continuous-time system is of minimum phase), so that the cyber-physical system becomes vulnerable to `sampling zero dynamics attack.' In this paper, we begin with its demonstration by a few examples. Then, we present an idea to protect the system by allocating those discrete-time zeros into stable ones. This idea is realized by employing the so-called `generalized hold' which replaces the zero-order-hold.

2018-02-28
Kaelbling, L. P., Lozano-Pérez, T..  2017.  Learning composable models of parameterized skills. 2017 IEEE International Conference on Robotics and Automation (ICRA). :886–893.

There has been a great deal of work on learning new robot skills, but very little consideration of how these newly acquired skills can be integrated into an overall intelligent system. A key aspect of such a system is compositionality: newly learned abilities have to be characterized in a form that will allow them to be flexibly combined with existing abilities, affording a (good!) combinatorial explosion in the robot's abilities. In this paper, we focus on learning models of the preconditions and effects of new parameterized skills, in a form that allows those actions to be combined with existing abilities by a generative planning and execution system.

2018-02-02
Mirkhanzadeh, B., Shao, C., Shakeri, A., Sato, T., Razo-Razo, M., Tacca, M., Fumagalli, A., Yamanaka, N..  2017.  A two-layer network Orchestrator offering trustworthy connectivity to a ROS-industrial application. 2017 19th International Conference on Transparent Optical Networks (ICTON). :1–4.

This paper describes an experiment carried out to demonstrate robustness and trustworthiness of an orchestrated two-layer network test-bed (PROnet). A Robotic Operating System Industrial (ROS-I) distributed application makes use of end-to-end flow services offered by PROnet. The PROnet Orchestrator is used to provision reliable end-to-end Ethernet flows to support the ROS-I application required data exchange. For maximum reliability, the Orchestrator provisions network resource redundancy at both layers, i.e., Ethernet and optical. Experimental results show that the robotic application is not interrupted by a fiber outage.

Kim, C..  2016.  Cyber-resilient industrial control system with diversified architecture and bus monitoring. 2016 World Congress on Industrial Control Systems Security (WCICSS). :1–6.

This paper focuses on exploitable cyber vulnerabilities in industrial control systems (ICS) and on a new approach of resiliency against them. Even with numerous metrics and methods for intrusion detection and mitigation strategy, a complete detection and deterrence of cyber-attacks for ICS is impossible. Countering the impact and consequence of possible malfunctions caused by such attacks in the safety-critical ICS's, this paper proposes new controller architecture to fail-operate even under compromised situations. The proposed new ICS is realized with diversification of hardware/software and unidirectional communication in alerting suspicious infiltration to upper-level management. Equipped with control bus monitoring, this operation-basis approach of infiltration detection would become a truly cyber-resilient ICS. The proposed system is tested in a lab hardware experimentation setup and on a cybersecurity test bed, DeterLab, for validation.

Ashok, A., Sridhar, S., McKinnon, A. D., Wang, P., Govindarasu, M..  2016.  Testbed-based performance evaluation of Attack Resilient Control for AGC. 2016 Resilience Week (RWS). :125–129.

The modern electric power grid is a complex cyber-physical system whose reliable operation is enabled by a wide-area monitoring and control infrastructure. Recent events have shown that vulnerabilities in this infrastructure may be exploited to manipulate the data being exchanged. Such a scenario could cause the associated control applications to mis-operate, potentially causing system-wide instabilities. There is a growing emphasis on looking beyond traditional cybersecurity solutions to mitigate such threats. In this paper we perform a testbed-based validation of one such solution - Attack Resilient Control (ARC) - on Iowa State University's PowerCyber testbed. ARC is a cyber-physical security solution that combines domain-specific anomaly detection and model-based mitigation to detect stealthy attacks on Automatic Generation Control (AGC). In this paper, we first describe the implementation architecture of the experiment on the testbed. Next, we demonstrate the capability of stealthy attack templates to cause forced under-frequency load shedding in a 3-area test system. We then validate the performance of ARC by measuring its ability to detect and mitigate these attacks. Our results reveal that ARC is efficient in detecting stealthy attacks and enables AGC to maintain system operating frequency close to its nominal value during an attack. Our studies also highlight the importance of testbed-based experimentation for evaluating the performance of cyber-physical security and control applications.

2018-01-10
Ahmed, C. M., Mathur, A. P..  2017.  Hardware Identification via Sensor Fingerprinting in a Cyber Physical System. 2017 IEEE International Conference on Software Quality, Reliability and Security Companion (QRS-C). :517–524.

A lot of research in security of cyber physical systems focus on threat models where an attacker can spoof sensor readings by compromising the communication channel. A little focus is given to attacks on physical components. In this paper a method to detect potential attacks on physical components in a Cyber Physical System (CPS) is proposed. Physical attacks are detected through a comparison of noise pattern from sensor measurements to a reference noise pattern. If an adversary has physically modified or replaced a sensor, the proposed method issues an alert indicating that a sensor is probably compromised or is defective. A reference noise pattern is established from the sensor data using a deterministic model. This pattern is referred to as a fingerprint of the corresponding sensor. The fingerprint so derived is used as a reference to identify measured data during the operation of a CPS. Extensive experimentation with ultrasonic level sensors in a realistic water treatment testbed point to the effectiveness of the proposed fingerprinting method in detecting physical attacks.