Biblio

This paper presents a novel method, combining new formulations and sampling, to improve the scalability of sum-of-squares (SOS) programming-based system verification. Region-of-attraction approximation problems are considered for polynomial, polynomial with generalized Lur'e uncertainty, and rational trigonometric multi-rigid-body systems. Our method starts by identifying that Lagrange multipliers, traditionally heavily used for S-procedures, are a major culprit of creating bloated SOS programs. In light of this, we exploit inherent system properties-continuity, convexity, and implicit algebraic structure-and reformulate the problems as quotient-ring SOS programs, thereby eliminating all the multipliers. These new programs are smaller, sparser, less constrained, yet less conservative. Their computation is further improved by leveraging a recent result on sampling algebraic varieties. Remarkably, solution correctness is guaranteed with just a finite (in practice, very small) number of samples. Altogether, the proposed method can verify systems well beyond the reach of existing SOS-based approaches (32 states); on smaller problems where a baseline is available, it computes tighter solution 2-3 orders of magnitude faster.

Technology and the use of online services are very prevalent across much of our everyday lives. As our digital interactions continue to grow, there is a need to improve public awareness of the risks to our personal online privacy and security. Designing for cyber security awareness has never been so important. In this work, we consider people's current impressions towards their privacy and security online. We also explore how abnormal network activity data can be visually conveyed to afford a heightened cyber security awareness. In detail, the paper documents the different effects of visual variables in an edge and node DoS visualisation to depict abnormally high volumes of traffic. The results from two studies show that people are generally becoming more concerned about their privacy and security online. Moreover, we have found that the more focus based visual techniques (i.e. blur) and geometry-based techniques (i.e. jaggedness and sketchiness) afford stronger impressions of uncertainty from abnormally high volumes of network traffic. In terms of security, these impressions and feelings alert in the end-user that something is not quite as it should be and hence develop a heightened cyber security awareness.

Trust is a fundamental factor in how users engage in interactions with Visual Analytics (VA) systems. While the importance of building trust to this end has been pointed out in research, the aspect that trust can also be misplaced is largely ignored in VA so far. This position paper addresses this aspect by putting trust calibration in focus – i.e., the process of aligning the user’s trust with the actual trustworthiness of the VA system. To this end, we present the trust continuum in the context of VA, dissect important trust issues in both VA systems and users, as well as discuss possible approaches that can build and calibrate trust.

Learning-enabled components (LECs) are widely used in cyber-physical systems (CPS) since they can handle the uncertainty and variability of the environment and increase the level of autonomy. However, it has been shown that LECs such as deep neural networks (DNN) are not robust and adversarial examples can cause the model to make a false prediction. The paper considers the problem of efficiently detecting adversarial examples in LECs used for regression in CPS. The proposed approach is based on inductive conformal prediction and uses a regression model based on variational autoencoder. The architecture allows to take into consideration both the input and the neural network prediction for detecting adversarial, and more generally, out-of-distribution examples. We demonstrate the method using an advanced emergency braking system implemented in an open source simulator for self-driving cars where a DNN is used to estimate the distance to an obstacle. The simulation results show that the method can effectively detect adversarial examples with a short detection delay.

Supply chain security threats pose new challenges to security risk modeling techniques for complex ICT systems such as the IoT. With established techniques drawn from attack trees and reliability analysis providing needed points of reference, graph-based analysis can provide a framework for considering the role of suppliers in such systems. We present such a framework here while highlighting the need for a component-centered model. Given resource limitations when applying this model to existing systems, we study various classes of uncertainties in model development, including structural uncertainties and uncertainties in the magnitude of estimated event probabilities. Using case studies, we find that structural uncertainties constitute a greater challenge to model utility and as such should receive particular attention. Best practices in the face of these uncertainties are proposed.

We study the incentives that independent self-interested agents have in forming a resilient supply chain network in the face of disruptions and competition. Competing suppliers are subject to yield uncertainty and congestion. Competing retailers make sourcing decisions based on price and reliability. Under yield uncertainty only, retailers–-benefiting from supply variance–-concentrate their links on a single supplier, counter to the idea that they should mitigate yield uncertainty by multi-sourcing. When congestion is added, the resulting networks resemble bipartite expanders known to be resilient, thus, providing the first example of endogenously formed resilient supply chains.

This study investigates the relationship between resilience of control systems to attacks and the information available to malicious attackers. Specifically, it is shown that control systems are guaranteed to be secure in an asymptotic manner by rendering reactions against potentially harmful actions covert. The behaviors of the attacker and the defender are analyzed through a repeated signaling game with an undisclosed belief under covert reactions. In the typical setting of signaling games, reactions conducted by the defender are supposed to be public information and the measurability enables the attacker to accurately trace transitions of the defender's belief on existence of a malicious attacker. In contrast, the belief in the game considered in this paper is undisclosed and hence common equilibrium concepts can no longer be employed for the analysis. To surmount this difficulty, a novel framework for decision of reasonable strategies of the players in the game is introduced. Based on the presented framework, it is revealed that any reasonable strategy chosen by a rational malicious attacker converges to the benign behavior as long as the reactions performed by the defender are unobservable to the attacker. The result provides an explicit relationship between resilience and information, which indicates the importance of covertness of reactions for designing secure control systems.

In the past few years, the malware industry has been thriving. Malware variants among the same malware family shared similar behavioural patterns or signatures reflecting their purpose. We propose an approach that combines support vector machine (SVM) classifiers and active learning by learning (ALBL) techniques to deal with insufficient labeled data in terms of the malware classification tasks. The proposed approach is evaluated with the malware family dataset from Microsoft Malware Classification Challenge (BIG 2015) on Kaggle. The results show that ALBL techniques can effectively boost the performance of our machine learning models and improve the quality of labeled samples.

One of the main threats to the underwater communication cables identified in the recent years is possible tampering or damage by malicious actors. This paper proposes a solution with explanation abilities to detect and investigate this kind of threat within the evidence theory framework. The reasoning scheme implements the traditional “opportunity-capability-intent” threat model to assess a degree to which a given vessel may pose a threat. The scenario discussed considers a variety of possible pieces of information available from different sources. A source quality model is used to reason with the partially reliable sources and the impact of this meta-information on the overall assessment is illustrated. Examples of uncertain relationships between the relevant variables are modelled and the constructed model is used to investigate the probability of threat of four vessels of different types. One of these cases is discussed in more detail to demonstrate the explanation abilities. Explanations about inference are provided thanks to sensitivity spaces in which the impact of the different pieces of information on the reasoning are compared.

We consider a two-player zero-sum network routing game in which a router wants to maximize the amount of legitimate traffic that flows from a given source node to a destination node and an attacker wants to block as much legitimate traffic as possible by flooding the network with malicious traffic. We address scenarios with asymmetric information, in which the router must reveal its policy before the attacker decides how to distribute the malicious traffic among the network links, which is naturally modeled by the notion of Stackelberg equilibria. The paper focuses on parallel networks, and includes three main contributions: we show that computing the optimal attack policy against a given routing policy is an NP-hard problem; we establish conditions under which the Stackelberg equilibria lead to no regret; and we provide a metric that can be used to quantify how uncertainty about the attacker's capabilities limits the router's performance.

We present a covert (low probability of detection) communication scheme that exploits the node multiplicity and channel variations in wireless broadcast networks. The transmitter hides the covert (private) message by superimposing it onto a non-covert (public) message such that the total transmission power remains the same whether or not the covert message is transmitted. It makes the detection of the covert message impossible unless the non-covert message is decoded. We exploit the multiplicity of non-covert messages (users) to provide a degree of freedom in choosing the non-covert message such that the total detection error probability (sum of the probability of false alarm and missed detection) is maximized. We also exploit the channel variation to minimize the throughput loss on the non-covert message by sending the covert message only when the transmission rate of the non-covert message is low. We show that the total detection error probability converges fast to 1 as the number of non-covert users increases and that the total detection error probability increases as the transmit power increases, without requiring a pre-shared secret among the nodes.

Following substantial advancements in stochastic classes of decision-making optimization problems, scenario-based stochastic optimization, robust\textbackslashtextbackslash distributionally robust optimization, and chance-constrained optimization have recently gained an increasing attention. Despite the remarkable developments in probabilistic forecast of uncertainties (e.g., in renewable energies), most approaches are still being employed in a univariate framework which fails to unlock a full understanding on the underlying interdependence among uncertain variables of interest. In order to yield cost-optimal solutions with predefined probabilistic guarantees, conditional and dynamic interdependence in uncertainty forecasts should be accommodated in power systems decision-making. This becomes even more important during the emergencies where high-impact low-probability (HILP) disasters result in remarkable fluctuations in the uncertain variables. In order to model the interdependence correlation structure between different sources of uncertainty in power systems during both normal and emergency operating conditions, this paper aims to bridge the gap between the probabilistic forecasting methods and advanced optimization paradigms; in particular, perdition regions are generated in the form of ellipsoids with probabilistic guarantees. We employ a modified Khachiyan's algorithm to compute the minimum volume enclosing ellipsoids (MVEE). Application results based on two datasets on wind and photovoltaic power are used to verify the efficiency of the proposed framework.

In an increasingly asymmetric context of both instability and permanent innovation, organizations demand new capacities and learning patterns. In this sense, supervisors have adopted the metaphor of the "sandbox" as a strategy that allows their regulated parties to experiment and test new proposals in order to study them and adjust to the established compliance frameworks. Therefore, the concept of the "sandbox" is of educational interest as a way to revindicate failure as a right in the learning process, allowing students to think, experiment, ask questions and propose ideas outside the known theories, and thus overcome the mechanistic formation rooted in many of the higher education institutions. Consequently, this article proposes the application of this concept for educational institutions as a way of resignifying what students have learned.

It is important to be able to establish formal performance bounds for autonomous systems. However, formal verification techniques require a model of the environment in which the system operates; a challenge for autonomous systems, especially those expected to operate over longer timescales. This paper describes work in progress to automate the monitor and repair of ROS-based autonomous robot software written for an apriori partially known and possibly incorrect environment model. A taint analysis method is used to automatically extract the dataflow sequence from input topic to publish topic, and instrument that code. A unique reinforcement learning approximation of MDP utility is calculated, an empirical and non-invasive characterization of the inherent objectives of the software designers. By comparing design (a-priori) utility with deploy (deployed system) utility, we show, using a small but real ROS example, that it's possible to monitor a performance criterion and relate violations of the criterion to parts of the software. The software is then patched using automated software repair techniques and evaluated against the original off-line utility.

With the development of augmented reality(AR) technology and location-based service (LBS) technology, combining AR with LBS will create a new way of life and socializing. In AR, users may consider the privacy and security of data. In LBS, the leakage of user location privacy is an important threat to LBS users. Therefore, it is very important for privacy management of positioning information and user location privacy to avoid loopholes and abuse. In this review, the concepts and principles of AR technology and LBS would be introduced. The existing privacy measurement and privacy protection framework would be analyzed and summarized. Also future research direction of location privacy protection would be discussed.

As a promising solution of spectrum shortage, spectrum sharing has received tremendous interests recently. However, under different sharing policies of different licensees, the shared spectrum is heterogeneous both temporally and spatially, and is usually uncertain due to the unpredictable activities of incumbent users. In this paper, considering the spectrum uncertainty, we propose a spectrum sharing based delay-tolerant traffic off-loading (SDTO) scheme. To capture the available heterogeneous shared bands, we adopt a mesh cognitive radio network and employ the multi-hop transmission mode. To statistically guarantee the end-to-end (E2E) session request under the uncertain spectrum supply, we formulate the SDTO scheme into a stochastic optimization problem, which is transformed into a mixed integer nonlinear programming (MINLP) problem. Then, a coarse-fine search based iterative heuristic algorithm is proposed to solve the MINLP problem. Simulation results demonstrate that the proposed SDTO scheme can well schedule the network resource with an E2E session guarantee.

Adversary emulation is an offensive exercise that provides a comprehensive assessment of a system’s resilience against cyber attacks. However, adversary emulation is typically a manual process, making it costly and hard to deploy in cyber-physical systems (CPS) with complex dynamics, vulnerabilities, and operational uncertainties. In this paper, we develop an automated, domain-aware approach to adversary emulation for CPS. We formulate a Markov Decision Process (MDP) model to determine an optimal attack sequence over a hybrid attack graph with cyber (discrete) and physical (continuous) components and related physical dynamics. We apply model-based and model-free reinforcement learning (RL) methods to solve the discrete-continuous MDP in a tractable fashion. As a baseline, we also develop a greedy attack algorithm and compare it with the RL procedures. We summarize our findings through a numerical study on sensor deception attacks in buildings to compare the performance and solution quality of the proposed algorithms.

The current trend of IoT user is toward the use of services and data externally due to voluminous processing, which demands resourceful machines. Instead of relying on the cloud of poor connectivity or a limited bandwidth, the IoT user prefers to use a cloudlet-based fog computing. However, the choice of cloudlet is solely dependent on its trust and reliability. In practice, even though a cloudlet possesses a required trusted platform module (TPM), we argue that the presence of a TPM is not enough to make the cloudlet trustworthy as the TPM supports only the primitive security of the bootstrap. Besides uncertainty in security, other uncertain conditions of the network (e.g. network bandwidth, latency and expectation time to complete a service request for cloud-based services) may also prevail for the cloudlets. Therefore, in order to evaluate the trust value of multiple cloudlets under uncertainty, this paper broadly proposes the empirical process for evaluation of trust. This will be followed by a measure of trust-based reputation of cloudlets through computational intelligence such as fuzzy logic and ant colony optimization (ACO). In the process, fuzzy logic-based inference and membership evaluation of trust are presented. In addition, ACO and its pheromone communication across different colonies are being modeled with multiple cloudlets. Finally, a measure of affinity or popular trust and reputation of the cloudlets is also proposed. Together with the context of application under multiple cloudlets, the computationally intelligent approaches have been investigated in terms of performance. Hence the contribution is subjected towards building a trusted cloudlet-based fog platform.

Moving target defense (MTD) suggests a game-changing way of enhancing web security by increasing uncertainty and complexity for attackers. A good number of web MTD techniques have been investigated to counter various types of web attacks. However, in most MTD techniques, only fixed attributes of the attack surface are shifted, leaving the rest exploitable by the attackers. Currently, there are few mechanisms to support the whole attack surface movement and solve the partial coverage problem, where only a fraction of the possible attributes shift in the whole attack surface. To address this issue, this paper proposes a Web Gene Tree (WGT) based MTD mechanism. The key point is to extract all potential exploitable key attributes related to vulnerabilities as web genes, and mutate them using various MTD techniques to withstand various attacks. Experimental results indicate that, by randomly shifting web genes and diversely inserting deceptive ones, the proposed WGT mechanism outperforms other existing schemes and can significantly improve the security of web applications.

While internet technologies are developing day by day, threats against them are increasing at the same speed. One of the most serious and common types of attacks is Distributed Denial of Service (DDoS) attacks. The DDoS intrusion detection approach proposed in this study is based on fuzzy logic and entropy. The network is modeled as a graph and graphics-based features are used to distinguish attack traffic from non-attack traffic. Fuzzy clustering is applied based on these properties to indicate the tendency of IP addresses or port numbers to be in the same cluster. Based on this uncertainty, attack and non-attack traffic were modeled. The detection stage uses the fuzzy relevance function. This algorithm was tested on real data collected from Boğaziçi University network.

Learning-based approaches often outperform hand-coded algorithmic solutions for many problems in robotics. However, learning long-horizon tasks on real robot hardware can be intractable, and transferring a learned policy from simulation to reality is still extremely challenging. We present a novel approach to model-free reinforcement learning that can leverage existing sub-optimal solutions as an algorithmic prior during training and deployment. During training, our gated fusion approach enables the prior to guide the initial stages of exploration, increasing sample-efficiency and enabling learning from sparse long-horizon reward signals. Importantly, the policy can learn to improve beyond the performance of the sub-optimal prior since the prior's influence is annealed gradually. During deployment, the policy's uncertainty provides a reliable strategy for transferring a simulation-trained policy to the real world by falling back to the prior controller in uncertain states. We show the efficacy of our Multiplicative Controller Fusion approach on the task of robot navigation and demonstrate safe transfer from simulation to the real world without any fine-tuning. The code for this project is made publicly available at https://sites.google.com/view/mcf-nav/home.

Cyber threat intelligence (CTI) is an effective approach to improving cyber security of businesses. CTI provides information of business contexts affected by cyber threats and the corresponding countermeasures. If businesses can identify relevant CTI, they can take defensive actions before the threats, described in the relevant CTI, take place. However, businesses still lack knowledge to help identify relevant CTI. Furthermore, information in real-world systems is usually vague, imprecise, inconsistent and incomplete. This paper defines a business object that is a business context surrounded by CTI. A business object models the connection knowledge for CTI onto the business. To assemble the business objects, this paper proposes a novel representation of business oriented CTI and a system used for constructing and extracting the business objects. Generalised grey numbers, fuzzy sets and rough sets are used for the representation, and set approximations are used for the extraction of the business objects. We develop a prototype of the system and use a case study to demonstrate how the system works. We then conclude the paper together with the future research directions.

Multi-Agent Task Allocation is a pre-requisite for many autonomous, real-world systems because of the need for intelligent task assignment amongst a team for maximum efficiency. Similarly, agent failure, task, failure, and a lack of state information are inherent challenges when operating in complex environments. Many existing solutions make simplifying assumptions regarding the modeling of these factors, e.g., Markovian state information. However, it is not clear that this is always the appropriate approach or that results from these approaches are necessarily representative of performance in the natural world. In this work, we demonstrate that there exists a class of problems for which non-Markovian state modeling is beneficial. Furthermore, we present and characterize a novel heuristic for task allocation that incorporates realistic state and uncertainty modeling in order to improve performance. Our quantitative analysis, when tested in a simulated search and rescue (SAR) mission, shows a decrease in performance of more than 57% when a representative method with Markovian assumptions is tested in a non-Markovian setting. Our novel heuristic has shown an improvement in performance of 3-15%, in the same non-Markovian setting, by modeling probabilistic failure and making fewer assumptions.

Strategic management and security risk management are part of the general government of the country, and therefore it is not possible to examine it separately and even if it was, one separate examination would not have give us a complete idea of how to implement this process. A modern understanding of the strategic security management requires not only continuous efforts to improve security policy formation and implementation but also new approaches and particular solutions to modernize the security system by making it adequate to the requirements of the dynamic security environment.

The cybersecurity of the modern control system is becoming a critical issue to the cyber-physical systems (CPS). Mitigating potential cyberattacks in the control system is an important concern in the controller design to enhance the resilience of the overall system. This paper presents a novel robust control architecture for the PV converter system to mitigate the sensor and actuator attack and reduce the influence of the system uncertainty. The sensor and actuator attack is a vicious attack scenario when the attack signals are injected into the sensor and actuator in a CPS simultaneously. A p-synthesis robust control architecture is proposed to mitigate the sensor and actuator attack and limit the system uncertainty perturbations in a DC-DC photovoltaic (PV) converter. A new system state matrix and control architecture is presented by integrating the original system state, injected attack signals and system uncertainty perturbations. In the case study, the proposed μ-synthesis robust controller exhibits a robust performance in the face of the sensor and actuator attack.