As Machine Learning (ML) algorithms are deployed to solve a wide variety of tasks in today’s world, data poisoning attack poses a significant threat to ML applications. Although numerous defence algorithms against data poisoning attack have been proposed and shown to be effective, most defence algorithms are analyzed under the assumption of fixed attack strategies, without accounting for the strategic interactions between the attacker and the defender. In this work, we perform game theoretic analysis of defence algorithms against data poisoning attacks on Machine Learning. We study the defence strategy as a competitive game between the defender and the adversary and analyze the game characteristics for several defence algorithms. We propose a game model for the poisoning attack scenario, and prove the characteristics of the Nash Equilibrium (NE) defence strategy for all distance-based defence algorithms. Based on the NE characteristics, we develop an efficient algorithm to approximate for the NE defence strategy. Using fixed attack strategies as the benchmark, we then experimentally evaluate the impact of strategic interactions in the game model. Our approach does not only provide insights about the effectiveness of the analyzed algorithms under optimal poisoning attacks, but also serves as a method for the modellers to determine capable defence algorithms and optimal strategies to employ on their ML models. / Thesis / Master of Science (MSc) / As Machine Learning (ML) algorithms are deployed to solve a wide variety of tasks in today’s world, data poisoning attack poses a significant threat to ML applications. In this work, we study the defence against poisoning attack scenario as a competitive game between the defender and the adversary and analyze the game characteristics for several defence algorithms. Our goal is to identify the optimal defence strategy against poisoning attacks, even when the adversary responds optimally to the defence strategy. We propose a game model for the poisoning attack scenario, and develop an efficient algorithm to approximate for the Nash Equilibrium defence strategy. Our approach does not only provide insights about the effectiveness of the analyzed algorithms under optimal poisoning attacks, but also serves as a method for the modellers to determine capable defence algorithms and optimal strategies to employ on their ML models.