Biblio

Cybersecurity for complex systems operating in cyber-physical environment is becoming more and more critical because of the increasing cyber threats and systems' vulnerabilities. Security by design is quite an important method to ensure the systems' normal operations and services supply. For the aim of coping with cyber-attack affections properly, this paper studies the resilient security control issue for time-varying delay systems in cyber-physical environment with state estimation and moving defense approach. Time-varying delay factor induced by communication and network transmission, or data acquisition and processing, or certain cyber-attacks, is considered. To settle the cyber-attacks from the perspective of system control, a dynamic system model considering attacks is presented, and the corresponding switched control model with time-varying delay against attacks is formulated. Then the state estimator for system states is designed to overcome the problem that certain states cannot be measured directly. Estimated states serve as the input of the resilient security controller. Sufficient conditions of the stability of the observer and control system are derived out with the Lyapunov stability analysis method jointly. A moving defense strategy based on anomaly detection and random switching is presented, in which an optimization problem for calculating the proper switching probability of each candidate actuator-controller pair is given. Simulation experimental results are shown to illustrate the effectiveness of the presented scheme.

In this paper, the distributed security control problem of connected vehicle systems (CVSs) is investigated under denial of service (DoS) attacks and uncertain dynamics. DoS attacks usually block communication channels, resulting in the vehicle inability to receive data from the neighbors. In severe cases, it will affect the control performance of CVSs and even cause vehicle collision and life threats. In order to keep the vehicle platoon stable when the DoS attacks happen, we introduce a random characteristic to describe the impact of the packet loss behavior caused by them. Dependent on the length of the lost packets, we propose a security platoon control protocol to deal with it. Furthermore, the security platoon control problem of CVSs is transformed into a stable problem of Markov jump systems (MJSs) with uncertain parameters. Next, the Lyapunov function method and linear matrix inequations (LMI) are used to analyze the internal stability and design controller. Finally, several simulation results are presented to illustrate the effectiveness of the proposed method.

Dynamic memory allocators are critical components of modern systems, and developers strive to find a balance between their performance and their security. Unfortunately, vulnerable allocators are routinely abused as building blocks in complex exploitation chains. Most of the research regarding memory allocators focuses on popular and standardized heap libraries, generally used by high-end devices such as desktop systems and servers. However, dynamic memory allocators are also extensively used in embedded systems but they have not received much scrutiny from the security community.In embedded systems, a raw firmware image is often the only available piece of information, and finding heap vulnerabilities is a manual and tedious process. First of all, recognizing a memory allocator library among thousands of stripped firmware functions can quickly become a daunting task. Moreover, emulating firmware functions to test for heap vulnerabilities comes with its own set of challenges, related, but not limited, to the re-hosting problem.To fill this gap, in this paper we present HEAPSTER, a system that automatically identifies the heap library used by a monolithic firmware image, and tests its security with symbolic execution and bounded model checking. We evaluate HEAPSTER on a dataset of 20 synthetic monolithic firmware images — used as ground truth for our analyses — and also on a dataset of 799 monolithic firmware images collected in the wild and used in real-world devices. Across these datasets, our tool identified 11 different heap management library (HML) families containing a total of 48 different variations. The security testing performed by HEAPSTER found that all the identified variants are vulnerable to at least one critical heap vulnerability. The results presented in this paper show a clear pattern of poor security standards, and raise some concerns over the security of dynamic memory allocators employed by IoT devices.

This contribution provides the implementation of a digital twin-based assistance system to be used in future control rooms. By applying parameter estimation methods, the dynamic model in the digital twin is an accurate representation of the physical system. Therefore, a dynamic security assessment (DSA) that is highly dependent on a correctly parameterized dynamic model, can give more reliable information to a system operator in the control room. The assistance system is studied on the Cigré TB 536 benchmark system with an obscured set of machine parameters. Through the proposed parameter estimation approach the original parameters could be estimated, changing, and increasing the statement of the DSA in regard to imminent instabilities.

Power system security assessment is a major issue among the fundamental functions needed for the proper power systems operation. In order to perform the security evaluation, the contingency analysis is a key component. However, the dynamic evolution of power systems during the past decades led to the necessity of novel techniques to facilitate this task. In this paper, power systems security is defined based on the N-l contingency analysis. An artificial neural network approach is proposed to ensure the fast evaluation of power systems security. In this regard, the IEEE 14 bus transmission system is used to verify the performance of the proposed model, the results showing high efficiency subject to multiple evaluation metrics.

We present an online framework for learning and updating security policies in dynamic IT environments. It includes three components: a digital twin of the target system, which continuously collects data and evaluates learned policies; a system identification process, which periodically estimates system models based on the collected data; and a policy learning process that is based on reinforcement learning. To evaluate our framework, we apply it to an intrusion prevention use case that involves a dynamic IT infrastructure. Our results demonstrate that the framework automatically adapts security policies to changes in the IT infrastructure and that it outperforms a state-of-the-art method.

To ensure dynamic and transient angle and load stability in order to maintain the power system security is a major task of the power Engineer. FACTS Controllers are most effective devices to ensure system security by enhancing the stability margins with reactive power support all over the power system network. The major shunt compensation devices of FACTS are SVC and STATCOM. This article dispenses the modelling and simulation of both the shunt devices viz. Oneis the Static Synchronous Compensator (STATCOM) and the other is Static Var Compensator (SVC). The small signal models of these devices have been derived from the first principles and obtained the transfer function models of weak and strong power systems. The weak power system has the Short Circuit Ratio (SCR) is about less than 3 and that of the strong power system has the SCR of more than 5. The performance of the both weak and strong power systems has been evaluated with time and frequency responses. The dynamic response is obtained with the exact models for both weak and strong systems, subsequently the root locus plots as well as bode plots have been obtained with MATLAB Programs and evaluated the performance of these devices and comparison is made. The Stability margins of both the systems with SVC and STATCOM have been obtained from the bode plots. The dynamic behaviour of the both kinds of power systems have been assessed with time responses of SVC and STATCOM models. All of these results viz. dynamic response, root locus and bode plots proves the superiority of the STATCOM over SVC with indices, viz. peak overshoot, settling time, gain margin and phase margins. The dynamic, steady state performance indices obtained from time response and bode plots proves the superior performance of STATCOM.

With the development of the information age, the process of global networking continues to deepen, and the cyberspace security has become an important support for today’s social functions and social activities. Web applications which have many security risks are the most direct interactive way in the process of the Internet activities. That is why the web applications face a large number of network attacks. Interpretive dynamic programming languages are easy to lean and convenient to use, they are widely used in the development of cross-platform web systems. As well as benefit from these advantages, the web system based on those languages is hard to detect errors and maintain the complex system logic, increasing the risk of system vulnerability and cyber threats. The attack defense of systems based on interpretive dynamic programming languages is widely concerned by researchers. Since the advance of endogenous security technologies, there are breakthroughs on the research of web system security. Compared with traditional security defense technologies, these technologies protect the system with their uncertainty, randomness and dynamism. Based on several common network attacks, the traditional system security defense technology and endogenous security technology of web application based on interpretive dynamic languages are surveyed and compared in this paper. Furthermore, the possible research directions of those technologies are discussed.

Transient stability accidents induced by converter-based resources have been emerging frequently around the world. In this paper, the transient stability of the grid-tied voltage source converter (VSC) system is studied through estimating the basin of attraction (BOA) based on the hyperplane or hypersurface method. Meanwhile, fault critical clearing times are estimated, based on the approximated BOA and numerical fault trajectory. Further, the dynamic security region (DSR), an important index in traditional power systems, is extended to power-electronics-dominated power systems in this paper. The DSR of VSC is defined in the space composed of active current references. Based on the estimated BOA, the single-VSC-infinite-bus system is taken as an example and its DSR is evaluated. Finally, all these analytical results are well verified by several numerical simulations in MATLAB/Simulink.

This study will be focused on efforts to increase the reliability of the Bangka Electricity System by designing the interconnection of the Bangka system with another system that is stronger and has a better energy mix, the Sumatra System. The novelty element in this research is the design of system protection using Special Protection System (SPS) as well as a different assessment method using the Fuzzy Technique This research will analyze the implementation of the SPS event-based and parameter-based as a new defense scheme by taking corrective actions to keep the system stable and reliable. These actions include tripping generators, loads, and reconfiguring the system automatically and quickly. The performance of this SPS will be tested on 10 contingency events with four different load profiles and the system response will be observed in terms of frequency stability, voltage, and rotor angle. From the research results, it can be concluded that the SPS performance on the Bangka-Sumatra Interconnection System has a better and more effective performance than the existing defense scheme, as evidenced by the results of dynamic security assessment (DSA) testing using Fuzzy Techniques.

Networked cyber-physical systems must balance the utility of communication for monitoring and control with the risks of revealing private information. Many of these networks, such as wireless communication, are vulnerable to eavesdrop-ping by illegitimate recipients. Obfuscation can hide information from eaves-droppers by ensuring their observations are ambiguous or misleading. At the same time, coordination with recipients can enable them to interpret obfuscated data. In this way, we propose an obfuscation framework for dynamic systems that ensures privacy against eavesdroppers while maintaining utility for legitimate recipients. We consider eavesdroppers unaware of obfuscation by requiring that their observations are consistent with the original system, as well as eaves-droppers aware of the goals of obfuscation by assuming they learn of the specific obfuscation implementation used. We present a method for bounded synthesis of solutions based upon distributed reactive synthesis and the synthesis of publicly-known obfuscators.

The load margin due to voltage instability and small-signal instability can be a valuable measure for the operator of the power system to ensure a continuous and safe supply of electricity. However, if this load margin was calculated without considering system operating requirements, then this margin may not be adequate. This article proposes an algorithm capable of providing the power system load margin considering the requirements of voltage stability, small-signal stability, and operational requirements, as limits of reactive power generation of synchronous generators in dynamic security assessment. Case studies were conducted in the 107-bus reduced order Brazilian system considering a list of contingencies and directions of load growth.

With the construction of power information network, the power grid has built a security protection system based on boundary protection. However, with the continuous advancement of the construction of the power Internet of Things, a large number of power Internet of Things terminals need to connect to the power information network through the public network, which have an impact on the existing security protection system of the power grid. This article analyzes the characteristics of the border protection model commonly used in network security protection. Aiming at the lack of security protection capabilities of this model, a zero-trust security architecture-based power Internet of Things network security protection model is proposed. Finally, this article analyzes and studies the application of zero trust in the power Internet of Things.

The widely adopted dynamic line rating (DLR) mechanism can improve the operation efficiency for industrial and commercial power systems. However, the predicted environmental parameters used in DLR bring great uncertainty to transmission line capacity estimation and may introduce system security risk if over-optimistic estimation is adopted in the operation process, which could affect the electrical safety of industrial and commercial power systems in multiple cases. Therefore, it becomes necessary to establish a system operation security assessment model to reduce the risk and provide operational guidance to enhance electrical safety. This paper aims to solve the electrical safety problems caused by the transmission line under DLR mechanism. An operation security assessment method of transmission lines considering DLR uncertainty is proposed to visualize the safety margin under the given operation strategy and optimally setting transmission line capacity while taking system safety into account. With the help of robust optimization (RO) techniques, the uncertainty is characterized and a risk-averse transmission line rating guidance can be established to determine the safety margin of line capacity for system operation. In this way, the operational security for industrial and commercial power systems can be enhanced by reducing the unsafe conditions while the operational efficiency benefit provided by DLR mechanism still exist.

Differential evolution algorithm is an efficient computational method that uses population crossover and variation to achieve high-quality solutions. The algorithm is simple in principle and fast in solving global solutions, so it has been widely used in complex optimization problems. In this paper, we applied the differential evolution algorithm to a time-delay dynamic system for microbial fermentation of 1,3-propanediol and obtained an average error of 22.67% comparing to baseline error of 48.53%.

In this study, we prove strong stability for a typical time-varying nonlinear dynamic system in batch culture, which is hard to obtain analytical solutions and equilibrium points. To this end, firstly, we construct a linear variational system to the nonlinear dynamic system. Secondly, we give a proof that the fundamental matrix solution to this dynamic system is bounded. Combined with the above two points, the strong stability for the nonlinear dynamic system is proved.

Ubiquitous Electric Internet of Things (UEIoT) is the next generation electrical energy networks. The distributed and open structure of UEIoT is weak and vulnerable to security threats. To solve the security problem of UEIoT terminal, in this paper, the interaction between smart terminals and the malicious attackers in UEIoT as a differential game is investigated. A complex decision-making process and interactions between the smart terminal and attackers are analyzed. Through derivation and analysis of the model, an algorithm for the optimal defense strategy of UEIoT is designed. The results lay a theoretical foundation, which can support UEIoT make a dynamic strategy to improve the defensive ability.

Continuous Integration (CI) and Continuous Delivery (CD) have become a well-known practice in DevOps to ensure fast delivery of new features. This is achieved by automatically testing and releasing new software versions, e.g. multiple times per day. However, classical security management techniques cannot keep up with this quick Software Development Life Cycle (SDLC). Nonetheless, guaranteeing high security quality of software systems has become increasingly important. The new trend of DevSecOps aims to integrate security techniques into existing DevOps practices. Especially, the automation of security testing is an important area of research in this trend. Although plenty of literature discusses security testing and CI/CD practices, only a few deal with both topics together. Additionally, most of the existing works cover only static code analysis and neglect dynamic testing methods. In this paper, we present an approach to integrate three automated dynamic testing techniques into a CI/CD pipeline and provide an empirical analysis of the introduced overhead. We then go on to identify unique research/technology challenges the DevSecOps communities will face and propose preliminary solutions to these challenges. Our findings will enable informed decisions when employing DevSecOps practices in agile enterprise applications engineering processes and enterprise security.

This work introduces methods that unlock a series of applications for decision trees and neural networks in power system optimization. Capturing constraints that were impossible to capture before in a scalable way, we use decision trees (or neural networks) to extract an accurate representation of the non-convex feasible region which is characterized by both algebraic and differential equations. Applying an exact transformation, we convert the information encoded in the decision trees and the neural networks to linear decision rules that we incorporate as conditional constraints in an optimization problem (MILP or MISOCP). Our approach introduces a framework to unify security considerations with electricity market operations, capturing not only steady-state but also dynamic stability constraints in power system optimization, and has the potential to eliminate redispatching costs, leading to savings of millions of euros per year.

In this extended abstract, we outline an approach for security certification of products or services for modern commercial systems that are characterized by agile development, the integration of development and operations, and high dynamics of system features and structures. The proposed scheme rather evaluates the processes applied in development and operations than investigates into the validity of the product properties itself. We argue that the resulting claims are still suitable to increase the confidence in the security of products and services resulting from such processes.

Dealing with algorithms, which process large amount of similar data by using significant number of small and various sizes of memory allocation/de-allocation in a dynamic yet deterministic way, is an important issue for soft real-time systems designs. In order to improve the response time, efficiency and security of this kind of processing, we propose a software-based memory management method based on hierarchy of shared memory pools, which could be used to replace standard heap management mechanism of the operating system for some cases. Implementation of this memory management scheme can allocate memory through processing allocation/de-allocation requests of required space. Lockable implementation of this model can safely deal with the multi-threaded concurrent access. We also provide the results of experiments, according to which response time of test systems with soft time-bounded execution demand were considerably improved.

Dynamic security assessment (DSA) is to ensure the power system being operated under a secure condition that can withstand potential contingencies. DSA normally proceeds periodically on a 5 to 15 minutes basis, where the system security condition over a complete time interval is merely determined upon the system snapshot captured at the beginning of the interval. With high wind power penetration, the minute-to-minute variations of wind power can lead to more volatile power system states within a single DSA time interval. This paper investigates the intra-interval variation (IIV) phenomenon in power system online DSA and analyze whether the IIV problem is deserved attention in future DSA research and applications. An IIV-contaminated testing environment based on hierarchical Monte-Carlo simulation is developed to evaluate the practical IIV impacts on power system security and DSA performance. The testing results show increase in system insecurity risk and significant degradation in DSA accuracy in presence of IIV. This result draws attention to the IIV phenomenon in DSA of wind-energy power systems and calls for more robust DSA approach to mitigate the IIV impacts.

Existing security models are highly linear and fail to capture the rich interactions that occur across security technology, infrastructure, cybersecurity, and human/organizational components. In this work, we will leverage insights from resilience science, complex system theory, and network theory to develop a next-generation security model based on these interactions to address challenges in complex, nonlinear risk environments and against innovative and disruptive technologies. Developing such a model is a key step forward toward a dynamic security paradigm (e.g., shifting from detection to anticipation) and establishing the foundation for designing next-generation physical security systems against evolving threats in uncontrolled or contested operational environments.

Power system security assessment and enhancement in grids with high penetration of renewables is critical for pragmatic power system planning. Static Security Assessment (SSA) is a fast response tool to assess system stability margins following considerable contingencies assuming post fault system reaches a steady state. This paper presents a contingency ranking methodology using static security indices to rank credible contingencies considering severity. A Modified IEEE 9 bus system integrating renewables was used to test the approach. The static security indices used independently provides accurate results in identifying severe contingencies but further assessment is needed to provide an accurate picture of static security assessment in an increased time frame of the steady state. The indices driven for static security assessment could accurately capture and rank contingencies with renewable sources but due to intermittency of the renewable source various contingency ranking lists are generated. This implies that using indices in future grids without consideration on intermittent nature of renewables will make it difficult for the grid operator to identify severe contingencies and assist the power system operator to make operational decisions. This makes it necessary to integrate the behaviour of renewables in security indices for practical application in real time security assessment.

In this paper, we discuss the methodology of generalizing the optimal control law from learned component tasks to unlearned composite tasks on Multi-Agent Systems (MASs), by using the linearity composition principle of linearly solvable optimal control (LSOC) problems. The proposed approach achieves both the compositionality and optimality of control actions simultaneously within the cooperative MAS framework in both discrete and continuous-time in a sample-efficient manner, which reduces the burden of re-computation of the optimal control solutions for the new task on the MASs. We investigate the application of the proposed approach on the MAS with coordination between agents. The experiments show feasible results in investigated scenarios, including both discrete and continuous dynamical systems for task generalization without resampling.