@article{wei_lu_wang_2018, title={On Characterizing Information Dissemination During City-Wide Cascading Failures in Smart Grid}, volume={12}, ISSN={["1937-9234"]}, DOI={10.1109/JSYST.2017.2763462}, abstractNote={Although the smart gird is expected to eliminate cascading failures with the help of real-time system monitoring and control, it is yet unknown whether its underlying communication network is fast and reliable enough to achieve this goal. In this paper, we take an in-depth study on this issue by addressing three specific questions: 1) what is the evolution process of information dissemination and fault propagation in the smart grid?; 2) how to quantify the impact of cascading failures?; and 3) what are the conditions that information dissemination becomes either a booster or an adversary in mitigating cascading failures? To answer these questions, we build an innovative framework, the cascading failure with communications framework, to consolidate both communication networks and power grids, and provide quantitative evaluation on the impact of cascading failures. By studying and observing the progress of cascading failures in two city-wide power grids, we find that information dissemination is not always the winner in the race against fault propagation. Particularly, while fast and reliable communications can help in mitigating the consequences of cascading failures, anomalies such as massage delays may weaken its capability. Moreover, severely under-achieved communications, counter-intuitively, can even exacerbate the consequence of cascading failures.}, number={4}, journal={IEEE SYSTEMS JOURNAL}, author={Wei, Mingkui and Lu, Zhuo and Wang, Wenye}, year={2018}, month={Dec}, pages={3404–3413} }
 @article{lu_wang_wang_2015, title={Camouflage Traffic: Minimizing Message Delay for Smart Grid Applications under Jamming}, volume={12}, ISSN={["1941-0018"]}, DOI={10.1109/tdsc.2014.2316795}, abstractNote={Smart grid is a cyber-physical system that integrates power infrastructures with information technologies. To facilitate efficient information exchange, wireless networks have been proposed to be widely used in the smart grid. However, the jamming attack that constantly broadcasts radio interference is a primary security threat to prevent the deployment of wireless networks in the smart grid. Hence, spread spectrum systems, which provide jamming resilience via multiple frequency and code channels, must be adapted to the smart grid for secure wireless communications, while at the same time providing latency guarantee for control messages. An open question is how to minimize message delay for timely smart grid communication under any potential jamming attack. To address this issue, we provide a paradigm shift from the case-by-case methodology, which is widely used in existing works to investigate well-adopted attack models, to the worst-case methodology, which offers delay performance guarantee for smart grid applications under any attack. We first define a generic jamming process that characterizes a wide range of existing attack models. Then, we show that in all strategies under the generic process, the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of traffic can in fact improve the worst-case delay performance. As a result, we demonstrate a lightweight yet promising system, transmitting adaptive camouflage traffic (TACT), to combat jamming attacks. TACT minimizes the message delay by generating extra traffic called camouflage to balance the network load at the optimum. Experiments show that TACT can decrease the probability that a message is not delivered on time in order of magnitude.}, number={1}, journal={IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING}, author={Lu, Zhuo and Wang, Wenye and Wang, Cliff}, year={2015}, pages={31–44} }
 @article{sun_wang_lu_2015, title={On Topology and Resilience of Large-Scale Cognitive Radio Networks Under Generic Failures}, volume={14}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2015.2404919}, abstractNote={It has been demonstrated that in wireless networks, blackholes, which are typically generated by isolated node failures, and augmented by failure correlations, can easily result in devastating impact on network performance. In order to address this issue, we focus on the topology of Cognitive Radio Networks (CRNs) because of their phenomenal benefits in improving spectrum efficiency through opportunistic communications. Particularly, we first define two metrics, namely the failure occurrence probability p and failure connection function g(·), to characterize node failures and their spreading properties, respectively. Then we prove that each blackhole is exponentially bounded based on percolation theory. By mapping failure spreading using a branching process, we further derive an upper bound on the expected size of blackholes. With the observations from our analysis, we are able to find a sufficient condition for a resilient CRN in the presence of blackholes through analysis and simulations.}, number={6}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Sun, Lei and Wang, Wenye and Lu, Zhuo}, year={2015}, month={Jun}, pages={3390–3401} }
 @inproceedings{lu_wang_wang_2014, title={How can botnets cause storms? Understanding the evolution and impact of mobile botnets}, DOI={10.1109/infocom.2014.6848085}, abstractNote={A botnet in mobile networks is a collection of compromised nodes due to mobile malware, which are able to perform coordinated attacks. Different from Internet botnets, mobile botnets do not need to propagate using centralized infrastructures, but can keep compromising vulnerable nodes in close proximity and evolving organically via data forwarding. Such a distributed mechanism relies heavily on node mobility as well as wireless links, therefore breaks down the underlying premise in existing epidemic modeling for Internet botnets. In this paper, we adopt a stochastic approach to study the evolution and impact of mobile botnets. We find that node mobility can be a trigger to botnet propagation storms: the average size (i.e., number of compromised nodes) of a botnet increases quadratically over time if the mobility range that each node can reach exceeds a threshold; otherwise, the botnet can only contaminate a limited number of nodes with average size always bounded above. This also reveals that mobile botnets can propagate at the fastest rate of quadratic growth in size, which is substantially slower than the exponential growth of Internet botnets. To measure the denial-of-service impact of a mobile botnet, we define a new metric, called last chipper time, which is the last time that service requests, even partially, can still be processed on time as the botnet keeps propagating and launching attacks. The last chipper time is identified to decrease at most on the order of 1/√B, where B is the network bandwidth. This result reveals that although increasing network bandwidth can help with mobile services; at the same time, it can indeed escalate the risk for services being disrupted by mobile botnets.}, booktitle={2014 proceedings ieee infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2014}, pages={1501–1509} }
 @article{lu_wang_wang_2014, title={Modeling, Evaluation and Detection of Jamming Attacks in Time-Critical Wireless Applications}, volume={13}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2013.146}, abstractNote={Recently, wireless networking for emerging cyber-physical systems, in particular the smart grid, has been drawing increasing attention in that it has broad applications for time-critical message delivery among electronic devices on physical infrastructures. However, the shared nature of wireless channels unavoidably exposes the messages in transit to jamming attacks, which broadcast radio interference to affect the network availability of electronic equipments. An important, yet open research question is how to model and detect jamming attacks in such wireless networks, where communication traffic is more time-critical than that in conventional data-service networks, such as cellular and WiFi networks. In this paper, we aim at modeling and detecting jamming attacks against time-critical wireless networks with applications to the smart grid. In contrast to communication networks where packets-oriented metrics, such as packet loss and throughput are used to measure the network performance, we introduce a new metric, message invalidation ratio, to quantify the performance of time-critical applications. Our modeling approach is inspired by the similarity between the behavior of a jammer who attempts to disrupt the delivery of a time-critical message and the behavior of a gambler who intends to win a gambling game. Therefore, by gambling-based modeling and real-time experiments, we find that there exists a phase transition phenomenon for successful time-critical message delivery under a variety of jamming attacks. That is, as the probability that a packet is jammed increases from 0 to 1, the message invalidation ratio first increases slightly, then increases dramatically to 1. Based on analytical and experimental results, we design the Jamming Attack Detection based on Estimation (JADE) scheme to achieve robust jamming detection, and implement JADE in a wireless network for power substations in the smart grid.}, number={8}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lu, Zhuo and Wang, Wenye and Wang, Cliff}, year={2014}, month={Aug}, pages={1746–1759} }
 @article{wang_lu_2013, title={Cyber security in the Smart Grid: Survey and challenges}, volume={57}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2012.12.017}, abstractNote={The Smart Grid, generally referred to as the next-generation power system, is considered as a revolutionary and evolutionary regime of existing power grids. More importantly, with the integration of advanced computing and communication technologies, the Smart Grid is expected to greatly enhance efficiency and reliability of future power systems with renewable energy resources, as well as distributed intelligence and demand response. Along with the silent features of the Smart Grid, cyber security emerges to be a critical issue because millions of electronic devices are inter-connected via communication networks throughout critical power facilities, which has an immediate impact on reliability of such a widespread infrastructure. In this paper, we present a comprehensive survey of cyber security issues for the Smart Grid. Specifically, we focus on reviewing and discussing security requirements, network vulnerabilities, attack countermeasures, secure communication protocols and architectures in the Smart Grid. We aim to provide a deep understanding of security vulnerabilities and solutions in the Smart Grid and shed light on future research directions for Smart Grid security.}, number={5}, journal={COMPUTER NETWORKS}, author={Wang, Wenye and Lu, Zhuo}, year={2013}, month={Apr}, pages={1344–1371} }
 @inproceedings{lu_wang_wang_2012, title={Hiding traffic with camouflage: Minimizing message delay in the smart grid under jamming}, DOI={10.1109/infcom.2012.6195760}, abstractNote={The smart grid is an emerging cyber-physical system that integrates power infrastructures with information technologies. In the smart grid, wireless networks have been proposed for efficient communications. However, the jamming attack that broadcasts radio interference is a primary security threat to prevent the deployment of wireless networks. Hence, spread spectrum systems with jamming resilience must be adapted to the smart grid to secure wireless communications. There have been extensive works on designing spread spectrum schemes to achieve feasible communication under jamming attacks. Nevertheless, an open question in the smart grid is how to minimize message delay for timely communication in power applications. In this paper, we address this problem in a wireless network with spread spectrum systems for the smart grid. By defining a generic jamming process that characterizes a wide range of existing jamming models, we show that the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of redundant traffic, called camouflage, can improve the worst-case delay performance. We demonstrate via experiments that transmitting camouflage traffic can decrease the probability that a message is not delivered on time in order of magnitude for smart grid applications.}, booktitle={2012 Proceedings IEEE infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2012}, pages={3066–3070} }
 @inproceedings{lu_wang_wang_2011, title={From jammer to gambler: Modeling and detection of jamming attacks against time-critical traffic}, DOI={10.1109/infcom.2011.5934989}, abstractNote={Time-critical wireless applications in emerging network systems, such as e-healthcare and smart grids, have been drawing increasing attention in both industry and academia. The broadcast nature of wireless channels unavoidably exposes such applications to jamming attacks. However, existing methods to characterize and detect jamming attacks cannot be applied directly to time-critical networks, whose communication traffic model differs from conventional models. In this paper, we aim at modeling and detecting jamming attacks against time-critical traffic. We introduce a new metric, message invalidation ratio, to quantify the performance of time-critical applications. A key insight that leads to our modeling is that the behavior of a jammer who attempts to disrupt the delivery of a time-critical message can be exactly mapped to the behavior of a gambler who tends to win a gambling game. We show via the gambling-based modeling and real-time experiments that there in general exists a phase transition phenomenon for a time-critical application under jamming attacks: as the probability that a packet is jammed increases from 0 to 1, the message invalidation ratio first increases slightly (even negligibly), then increases dramatically to 1. Based on analytical and experimental results, we further design and implement the JADE (Jamming Attack Detection based on Estimation) system to achieve efficient and robust jamming detection for time-critical wireless networks.}, booktitle={2011 proceedings ieee infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2011}, pages={1871–1879} }
 @inproceedings{lu_lu_wang_ma_2011, title={On network performance evaluation toward the smart grid: A case study of DNP3 over TCP/IP}, DOI={10.1109/glocom.2011.6134406}, abstractNote={The smart grid is the next-generation power system that incorporates power infrastructures with information technologies. In the smart grid, power devices are interconnected to support a variety of intelligent mechanisms, such as relay protection and demand response. To enable such mechanisms, messages must be delivered in a timely manner via network protocols. A cost-efficient and backward-compatible way for smart grid protocol design is to migrate current protocols in supervisory control and data acquisition (SCADA) systems to the smart grid. However, an open question is whether the performance of SCADA protocols can meet the timing requirements of smart grid applications. To address this issue, we establish a micro smart grid, Green Hub, to measure the delay performance of a predominant SCADA protocol, distributed network protocol 3.0 (DNP3) over TCP/IP. Our results show that although DNP3 over TCP/IP is widely considered as a smart grid communication protocol, it cannot be used in applications with delay constraints smaller than 16ms in Green Hub, such as relay protection. In addition, since DNP3 provides reliability mechanisms similar to TCP, we identify that such an overlapped design induces 50%-80% of the processing delay in embedded power devices. Our results indicate that DNP3 over TCP/IP can be further optimized in terms of delay efficiency, and a lightweight communication protocol is essential for time-critical smart grid applications.}, booktitle={2011 ieee global telecommunications conference (globecom 2011)}, author={Lu, X. and Lu, Z. and Wang, Wenye and Ma, J. F.}, year={2011} }
 @inproceedings{lu_wang_wang_2010, title={On order gain of backoff misbehaving nodes in CSMA/CA-based wireless networks}, DOI={10.1109/infcom.2010.5462002}, abstractNote={Backoff misbehavior, in which a wireless node deliberately manipulates its backoff time, can induce significant network problems, such as severe unfairness and denial-of-service. Although great progress has been made towards the design of countermeasures to backoff misbehavior, little attention has been focused on quantifying the gain of backoff misbehaviors. In this paper, we define and study two general classes of backoff misbehavior to assess the gain that misbehaving nodes can obtain. The first class, called continuous misbehavior, keeps manipulating the backoff time unless it is disabled by countermeasures. The second class is referred to as intermittent misbehavior, which tends to evade the detection by countermeasures by performing misbehavior sporadically. Our approach is to introduce a new performance metric, namely order gain, which is to characterize the performance benefits of misbehaving nodes in comparison to legitimate nodes. Through analytical studies, simulations, and experiments, we demonstrate the impact of a wide range of backoff misbehaviors on network performance with respect to the number of users in CSMA/CA-based wireless networks.}, booktitle={2010 proceedings ieee infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2010} }
 @inproceedings{lu_lu_wang_wang_2010, title={Review and evaluation of security threats on the communication networks in the smart grid}, DOI={10.1109/milcom.2010.5679551}, abstractNote={The smart grid, generally referred to as the next-generation power electric system, relies on robust communication networks to provide efficient, secure, and reliable information delivery. Thus, the network security is of critical importance in the smart grid. In this paper, we aim at classifying and evaluating the security threats on the communication networks in the smart grid. Based on a top-down analysis, we categorize the goals of potential attacks against the smart grid communication networks into three types: network availability, data integrity and information privacy. We then qualitatively analyze both the impact and feasibility of the three types of attacks. Moreover, since network availability is the top priority in the security objectives for the smart grid, we use experiments to quantitatively evaluate the impact of denial-of-service (DoS) attacks on a power substation network. Our work provides initial experimental data of DoS attacks against a power network and shows that the network performance degrades dramatically only when the DoS attack intensity approaches to the maximum.}, booktitle={Military communications conference, 2010 (milcom 2010)}, author={Lu, Z. and Lu, X. A. and Wang, Wenye and Wang, C.}, year={2010}, pages={1830–1835} }