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Conference Paper
Tian, Jue, Tan, Rui, Guan, Xiaohong, Liu, Ting.  2017.  Hidden Moving Target Defense in Smart Grids. Proceedings of the 2Nd Workshop on Cyber-Physical Security and Resilience in Smart Grids. :21–26.
Recent research has proposed a moving target defense (MTD) approach that actively changes transmission line susceptance to preclude stealthy false data injection (FDI) attacks against the state estimation of a smart grid. However, existing studies were often conducted under a less adversarial setting, in that they ignore the possibility that an alert attacker can also try to detect the activation of MTD and then cancel any FDI attack until they learn the new system configuration after MTD. Indeed, in this paper, we show that this can be achieved easily by the attacker. To improve the stealthiness of MTD against the attacker, we propose a hidden MTD approach that maintains the power flows of the whole grid after MTD. We develop an algorithm to construct the hidden MTD and analyze its feasibility condition when only a subset of transmission lines can adjust susceptance. Simulations are conducted to demonstrate the effectiveness of the hidden MTD against alert attackers under realistic settings.
Lou, Xin, Tran, Cuong, Yau, David K.Y., Tan, Rui, Ng, Hongwei, Fu, Tom Zhengjia, Winslett, Marianne.  2019.  Learning-Based Time Delay Attack Characterization for Cyber-Physical Systems. 2019 IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm). :1—6.
The cyber-physical systems (CPSes) rely on computing and control techniques to achieve system safety and reliability. However, recent attacks show that these techniques are vulnerable once the cyber-attackers have bypassed air gaps. The attacks may cause service disruptions or even physical damages. This paper designs the built-in attack characterization scheme for one general type of cyber-attacks in CPS, which we call time delay attack, that delays the transmission of the system control commands. We use the recurrent neural networks in deep learning to estimate the delay values from the input trace. Specifically, to deal with the long time-sequence data, we design the deep learning model using stacked bidirectional long short-term memory (LSTM) units. The proposed approach is tested by using the data generated from a power plant control system. The results show that the LSTM-based deep learning approach can work well based on data traces from three sensor measurements, i.e., temperature, pressure, and power generation, in the power plant control system. Moreover, we show that the proposed approach outperforms the base approach based on k-nearest neighbors.
Lakshminarayana, Subhash, Teng, Teo Zhan, Yau, David K. Y., Tan, Rui.  2017.  Optimal Attack Against Cyber-Physical Control Systems with Reactive Attack Mitigation. Proceedings of the Eighth International Conference on Future Energy Systems. :179–190.
This paper studies the performance and resilience of a cyber-physical control system (CPCS) with attack detection and reactive attack mitigation. It addresses the problem of deriving an optimal sequence of false data injection attacks that maximizes the state estimation error of the system. The results provide basic understanding about the limit of the attack impact. The design of the optimal attack is based on a Markov decision process (MDP) formulation, which is solved efficiently using the value iteration method. Using the proposed framework, we quantify the effect of false positives and mis-detections on the system performance, which can help the joint design of the attack detection and mitigation. To demonstrate the use of the proposed framework in a real-world CPCS, we consider the voltage control system of power grids, and run extensive simulations using PowerWorld, a high-fidelity power system simulator, to validate our analysis. The results show that by carefully designing the attack sequence using our proposed approach, the attacker can cause a large deviation of the bus voltages from the desired set-point. Further, the results verify the optimality of the derived attack sequence and show that, to cause maximum impact, the attacker must carefully craft his attack to strike a balance between the attack magnitude and stealthiness, due to the simultaneous presence of attack detection and mitigation.
Ghosh, Uttam, Dong, Xinshu, Tan, Rui, Kalbarczyk, Zbigniew, Yau, David K.Y., Iyer, Ravishankar K..  2016.  A Simulation Study on Smart Grid Resilience Under Software-Defined Networking Controller Failures. Proceedings of the 2Nd ACM International Workshop on Cyber-Physical System Security. :52–58.

Riding on the success of SDN for enterprise and data center networks, recently researchers have shown much interest in applying SDN for critical infrastructures. A key concern, however, is the vulnerability of the SDN controller as a single point of failure. In this paper, we develop a cyber-physical simulation platform that interconnects Mininet (an SDN emulator), hardware SDN switches, and PowerWorld (a high-fidelity, industry-strength power grid simulator). We report initial experiments on how a number of representative controller faults may impact the delay of smart grid communications. We further evaluate how this delay may affect the performance of the underlying physical system, namely automatic gain control (AGC) as a fundamental closed-loop control that regulates the grid frequency to a critical nominal value. Our results show that when the fault-induced delay reaches seconds (e.g., more than four seconds in some of our experiments), degradation of the AGC becomes evident. Particularly, the AGC is most vulnerable when it is in a transient following say step changes in loading, because the significant state fluctuations will exacerbate the effects of using a stale system state in the control.

Shen, Cheng, Liu, Tian, Huang, Jun, Tan, Rui.  2021.  When LoRa Meets EMR: Electromagnetic Covert Channels Can Be Super Resilient. 2021 IEEE Symposium on Security and Privacy (SP). :1304–1317.
Due to the low power of electromagnetic radiation (EMR), EM convert channel has been widely considered as a short-range attack that can be easily mitigated by shielding. This paper overturns this common belief by demonstrating how covert EM signals leaked from typical laptops, desktops and servers are decoded from hundreds of meters away, or penetrate aggressive shield previously considered as sufficient to ensure emission security. We achieve this by designing EMLoRa – a super resilient EM covert channel that exploits memory as a LoRa-like radio. EMLoRa represents the first attempt of designing an EM covert channel using state-of-the-art spread spectrum technology. It tackles a set of unique challenges, such as handling complex spectral characteristics of EMR, tolerating signal distortions caused by CPU contention, and preventing adversarial detectors from demodulating covert signals. Experiment results show that EMLoRa boosts communication range by 20x and improves attenuation resilience by up to 53 dB when compared with prior EM covert channels at the same bit rate. By achieving this, EMLoRa allows an attacker to circumvent security perimeter, breach Faraday cage, and localize air-gapped devices in a wide area using just a small number of inexpensive sensors. To countermeasure EMLoRa, we further explore the feasibility of uncovering EMLoRa's signal using energy- and CNN-based detectors. Experiments show that both detectors suffer limited range, allowing EMLoRa to gain a significant range advantage. Our results call for further research on the countermeasure against spread spectrum-based EM covert channels.