Hierarchical planning in security games: a game theoretic approach to strategic, tactical and operational decision making

2018-12-11In the presence of an intelligent adversary, game theoretic models such as security games, have proven to be effective tools for mitigating risks from exploitable gaps in protection and security protocols, as they model the strategic interaction between an adversary and defender, and allow the defender to plan the use of scarce or limited resources in the face of such an adversary. However, standard security game models have limited expressivity in the types of planning they allow the defender to perform, as they look only at the deployment and allocation of a fixed set of security resources. This ignores two very important planning problems which concern the strategic design of the security system and resources to deploy as well as the usability and implementation of the security protocols. When these problems appear in real world systems, significant losses in utility and efficiency of security protocols can occur if they are not dealt with in a principled way. ❧ To address these limitations, in this thesis I introduce a new hierarchical structure of planning problems for security games, dividing the problem into three levels of planning (i) Strategic Planning, which considers long term planning horizons, and decisions related to game design which constrain the possible defender strategies, (ii) Tactical Planning, which considers shorter term horizons, dealing with the deployment of resources, and selection of defender strategies subject to strategic level constraints and (iii) Operational Planning, dealing with implementation of strategies in real world setting. ❧ First, focusing on Strategic Planning, I address the design problem of selecting a set of resource and schedule types. I introduce a new yet fundamental problem, the Simultaneous Optimization of Resource Teams and Tactics (SORT) which models the coupled problem of both strategic and tactical planning, optimizing over both game design with respect to selection of resource types, as well as their deployment actual in the field. I provide algorithms for efficiently solving the SORT problem, which use hierarchical relaxations of the optimization problem to compute these strategic level investment decisions. I show that this more expressive model allows the defender to perform more fine grained decision making that results in significant gains in utility. Second, motivated by the relevance and hardness of security games with resource heterogeneity, I also address challenges in tactical planning by providing a framework for computing adaptive strategies with heterogeneous resources. Lastly, I look at the problem of operational planning, which has never been formally studied in the security game literature. I propose a new solution concept of operationalizable strategies, which randomize over an optimally chosen subset of pure strategies whose cardinality is selected by the defender. I show hardness of computing such operationalizable strategies and provide an algorithm for computingε-optimal equilibria which are operationalizable. ❧ In all of these problems, I am motivated by real world challenges, and developing solution methods that are usable in the real world. As such, much of this work has been in collaboration with organizations such as Panthera, WWF and other non-governmental organizations (NGOs), to help protect the national parks and wildlife against deforestation and poaching, and the TSA, to protect critical infrastructure such as our airports from terrorist attacks. Because of this, in addressing these three levels of planning, I develop solutions which are not only novel and academically interesting, but also deployable with a real world impact