T. Spyridopoulos, K. Maraslis, A. Mylonas, T. Tryfonas, G. Oikonomou, "A Game Theoretical Method for Cost-Benefit Analysis of Malware Dissemination Prevention", Information Security Journal: A Global Perspective, Taylor & Francis, 24(4-6), pp. 164-176, 2015
Literature in malware proliferation focuses on modeling and analyzing its spread dynamics. Epidemiology models, which are inspired by the characteristics of biological disease spread in human populations, have been used against this threat to analyze the way malware spreads in a network. This work presents a modified version of the commonly used epidemiology models Susceptible Infected Recovered (SIR) and Susceptible Infected Susceptible (SIS), which incorporates the ability to capture the relationships between nodes within a network, along with their effect on malware dissemination process. Drawing upon a model that illustrates the network’s behavior based on the attacker’s and the defender’s choices, we use game theory to compute optimal strategies for the defender to minimize the effect of malware spread, at the same time minimizing the security cost. We consider three defense mechanisms: patch, removal, and patch and removal, which correspond to the defender’s strategy and use probabilistically with a certain rate. The attacker chooses the type of attack according to its effectiveness and cost. Through the interaction between the two opponents we infer the optimal strategy for both players, known as Nash Equilibrium, evaluating the related payoffs. Hence, our model provides a cost-benefit risk management framework for managing malware spread in computer networks.
K. Maraslis, T. Spyridopoulos, G. Oikonomou, T. Tryfonas, M. Haghighi, "Application of a Game Theoretic Approach in Smart Sensor Data Trustworthiness Problems", in Proc. 30th IFIP TC 11 International Conference (SEC), ser. IFIP Advances in Information and Communication Technology, 455, pp. 601-615, 2015
In this work we present an Intrusion Detection (ID) and an Intrusion Prevention (IP) model for Wireless Sensor Networks (WSNs). The attacker’s goal is to compromise the deployment by causing nodes to report faulty sensory information. The defender, who is the WSN’s operator, aims to detect the presence of faulty sensor measurements (ID) and to subsequently recover compromised nodes (IP). In order to address the conflicting interests involved, we adopt a Game Theoretic approach that takes into consideration the strategies of both players and we attempt to identify the presence of Nash Equilibria in the two games. The results are then verified in two simulation contexts: Firstly, we evaluate the model in a middleware-based WSN which uses clustering over a bespoke network stack. Subsequently, we test the model in a simulated IPv6-based sensor deployment. According to the findings, the results of both simulation models confirm the results of the theoretic one.
T. Spyridopoulos, K. Maraslis, T. Tryfonas, G. Oikonomou, S. Li, "Managing Cyber Security Risks in Industrial Control Systems with Game Theory and Viable System Modelling", in Proc. 9th IEEE International System of Systems Engineering Conference (SOSE 2014), 2014
Cyber security risk management in Industrial Control Systems has been a challenging problem for both practitioners and the research community. Their proprietary nature along with the complexity of those systems renders traditional approaches rather insufficient and creating the need for the adoption of a holistic point of view. This paper draws upon the principles of the Viable System Model and Game Theory in order to present a novel systemic approach towards cyber security management in this field, taking into account the complex inter-dependencies and providing cost-efficient defence solutions.
T. Spyridopoulos, G. Karanikas, T. Tryfonas, G. Oikonomou, "A Game Theoretic Defence Framework Against DoS/DDoS Cyber Attacks", Computers & Security, Elsevier, 38, pp. 39-50, 2013
Game-theoretic approaches have been previously employed in the research area of network security in order to explore the interaction between an attacker and a defender during a Distributed Denial of Service (DDoS) attack scenario. Existing literature investigates payoffs and optimal strategies for both parties, in order to provide the defender with an optimal defence strategy. In this paper, we model a DDoS attack as a one-shot, non-cooperative, zero-sum game. We extend previous work by incorporating in our model a richer set of options available to the attacker compared to what has been previously achieved. We investigate multiple permutations in terms of the cost to perform an attack, the number of attacking nodes, malicious traffic probability distributions and their parameters. We analytically demonstrate that there exists a single optimal strategy available to the defender. By adopting it, the defender sets an upper boundary to attacker payoff, which can only be achieved if the attacker is a rational player. For all other attack strategies (those adopted by irrational attackers), attacker payoff will be lower than this boundary. We preliminary validate this model via simulations with the ns2 network simulator. The simulated environment replicates the analytical model's parameters and the results confirm our model's accuracy.
T. Spyridopoulos, G. Oikonomou, T. Tryfonas, M. Ge, "Game Theoretic Approach for Cost-Benefit Analysis of Malware Proliferation Prevention", in Proc. 28th IFIP TC-11 SEC 2013 International Information Security and Privacy Conference, pp. 28-41, 2013
Many existing research efforts in the field of malware proliferation aim at modelling and analysing its spread dynamics. Many malware dissemination models are based on the characteristics of biological disease spread in human populations. In this work, we utilise game theory in order to extend two very commonly used malware spread models (SIS and SIR) by incorporating defence strategies against malware proliferation. We consider three different security mechanisms, ``patch'', ``removal'' and ``patch and removal'' on which our model is based. We also propose a cost-benefit model that describes optimal strategies the defender could follow when cost is taken into account. Lastly, as a way of illustration, we apply our models on the well studied Code-Red worm.
P. Andriotis, T. Tryfonas, G. Oikonomou, T. Spyridopoulos, A. Zaharis, A. Martini, I. Askoxylakis, "On Two Different Methods for Steganography Detection in JPEG Images with Benford's Law", in Proc. 7th Scientific NATO Conference in Security and Protection of Information (SPI 2013), Brno, Czech Republic, pp. 3-14, 2013
The practice of steganography, which in a computer context usually means manipulating multimedia content to embed hidden messages, may be used by criminals worldwide to facilitate their communication instead of, or complementary to, encryption. There is even speculation that global terrorist groups have been using steganography to communicate in covert ways. This paper will introduce steganography and discuss practical aspects of its detection. It will also discuss two recently proposed methods for detecting whether hidden messages exist in JPEG images using Benford's Law. The Law describes the logarithmic distribution of leading digits in sets of naturally set numbers and has been used with success in detecting financial fraud and election rigging in the past. The first approach examines the lead digit distribution of the raw contents of the bytes of a suspect image, whilst the second examines the distribution of lead digits of quantised discrete cosine transform (DCT) coefficients of the JPEG encoding. Both methods produce fast and credible results and are supported by open source toolkits that can be used by law enforcement and investigative authorities worldwide.
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