Publications

2016
L. S. Marcolino, A. Lakshminarayanan, A. Yadav, and M. Tambe. 2016. “Simultaneous Influencing and Mapping for Health Interventions .” In 3rd Workshop on Expanding the Boundaries of Health Informatics Using AI (HIAI'16).Abstract
Influence Maximization is an active topic, but it was always assumed full knowledge of the social network graph. However, the graph may actually be unknown beforehand. For example, when selecting a subset of a homeless population to attend interventions concerning health, we deal with a network that is not fully known. Hence, we introduce the novel problem of simultaneously influencing and mapping (i.e., learning) the graph. We study a class of algorithms, where we show that: (i) traditional algorithms may have arbitrarily low performance; (ii) we can effectively influence and map when the independence of objectives hypothesis holds; (iii) when it does not hold, the upper bound for the influence loss converges to 0. We run extensive experiments over four real-life social networks, where we study two alternative models, and obtain significantly better results in both than traditional approaches.
2016_21_teamcore_aaai16.pdf
Shahrzad Gholami, Bryan Wilder, Matthew Brown, Arunesh Sinha, Nicole Sintov, and Milind Tambe. 2016. “SPECTRE: A Game Theoretic Framework for Preventing Collusion in Security Games (Demonstration) .” In International conference on Autonomous Agents and Multiagent Systems (AAMAS).Abstract
Several models have been proposed for Stackelberg security games (SSGs) and protection against perfectly rational and bounded rational adversaries; however, none of these existing models addressed the destructive cooperation mechanism between adversaries. SPECTRE (Strategic Patrol planner to Extinguish Collusive ThREats) takes into account the synergistic destructive collusion among two groups of adversaries in security games. This framework is designed for the purpose of efficient patrol scheduling for security agents in security games in presence of collusion and is mainly build up on game theoretic approaches, optimization techniques, machine learning methods and theories for human decision making under risk. The major advantage of SPECTRE is involving real world data from human subject experiments with participants on Amazon Mechanical Turk (AMT).
2016_19_teamcore_sgholami_demo_aamas2016.pdf
Nika Haghtalab, Fei Fang, Thanh H. Nguyen, Arunesh Sinha, Ariel D. Procaccia, and Milind Tambe. 2016. “Three Strategies to Success: Learning Adversary Models in Security Games .” In 25th International Joint Conference on Artificial Intelligence (IJCAI).Abstract
State-of-the-art applications of Stackelberg security games — including wildlife protection — offer a wealth of data, which can be used to learn the behavior of the adversary. But existing approaches either make strong assumptions about the structure of the data, or gather new data through online algorithms that are likely to play severely suboptimal strategies. We develop a new approach to learning the parameters of the behavioral model of a bounded rational attacker (thereby pinpointing a near optimal strategy), by observing how the attacker responds to only three defender strategies. We also validate our approach using experiments on real and synthetic data.
2016_27_teamcore_ijcai16_full.pdf
Thanh H. Nguyen, Debarun Kar, Matthew Brown, Arunesh Sinha, Albert Xin Jiang, and Milind Tambe. 2016. “Towards a Science of Security Games .” In New Frontiers of Multidisciplinary Research in STEAM-H (Book chapter) (edited by B Toni).Abstract
Security is a critical concern around the world. In many domains from counter-terrorism to sustainability, limited security resources prevent complete security coverage at all times. Instead, these limited resources must be scheduled (or allocated or deployed), while simultaneously taking into account the importance of different targets, the responses of the adversaries to the security posture, and the potential uncertainties in adversary payoffs and observations, etc. Computational game theory can help generate such security schedules. Indeed, casting the problem as a Stackelberg game, we have developed new algorithms that are now deployed over multiple years in multiple applications for scheduling of security resources. These applications are leading to real-world use-inspired research in the emerging research area of “security games”. The research challenges posed by these applications include scaling up security games to real-world sized problems, handling multiple types of uncertainty, and dealing with bounded rationality of human adversaries.
Fei Fang. 2016. “Towards Addressing Spatio-Temporal Aspects in Security Games ”.Abstract
Game theory has been successfully used to handle complex resource allocation and patrolling problems in security and sustainability domains. More specifically, real-world applications have been deployed for different domains based on the framework of security games, where the defender (e.g., security agency) has a limited number of resources to protect a set of targets from an adversary (e.g., terrorist). Whereas the first generation of security games research provided algorithms for optimizing security resources in mostly static settings, my thesis advances the state-of-the-art to a new generation of security games, handling massive games with complex spatio-temporal settings and leading to real-world applications that have fundamentally altered current practices of security resource allocation. Indeed, in many real-world domains, players act in a geographical space over time, and my thesis is then to expand the frontiers of security games and to deal with challenges in domains with spatio-temporal dynamics. My thesis provides the first algorithms and models for advancing key aspects of spatio-temporal challenges in security games, including (i) continuous time; (ii) continuous space; (iii) frequent and repeated attacks; (iv) complex spatial constraints. First, focusing on games where actions are taken over continuous time (for example games with moving targets such as ferries and refugee supply lines), I propose a new game model that accurately models the continuous strategy space for the attacker. Based on this model, I provide an efficient algorithm to calculate the defender’s optimal strategy using a compact representation for both the defender and the attacker’s strategy space. Second, for games where actions are taken over continuous space (for example games with forest land as a target), I provide an algorithm computing the optimal distribution of patrol effort. Third, my work addresses challenges with one key dimension of complexity – frequent and repeated attacks. Motivated by the repeated interaction of players in domains such as preventing poaching and illegal fishing, I introduce a novel game model that deals with frequent defender-adversary interactions and provide algorithms to plan effective sequential defender strategies. Furthermore, I handle complex spatial constraints that arise from the problem of designing optimal patrol strategy given detailed topographical information. My thesis work has led to two applications which have been deployed in the real world and have fundamentally altered previously used tactics, including one used by the US Coast Guard for protecting the Staten Island Ferry in New York City and another deployed in a protected area in Southeast Asia to combat poaching.
2016_30_teamcore_thesis_fang_2016.pdf
Thanh H. Nguyen, Arunesh Sinha, Shahrzad Gholami, Andrew Plumptre, Lucas Joppa, Milind Tambe, Margaret Driciru, Fred Wanyama, Aggrey Rwetsiba, Rob Critchlow, and Colin Beale. 2016. “CAPTURE: A New Predictive Anti-Poaching Tool for Wildlife Protection.” In 15th International Conference on Autonomous Agents and Multiagent Systems (AAMAS).Abstract
Wildlife poaching presents a serious extinction threat to many animal species. Agencies (“defenders”) focused on protecting such animals need tools that help analyze, model and predict poacher activities, so they can more effectively combat such poaching; such tools could also assist in planning effective defender patrols, building on the previous security games research. To that end, we have built a new predictive anti-poaching tool, CAPTURE (Comprehensive Anti-Poaching tool with Temporal and observation Uncertainty REasoning). CAPTURE provides four main contributions. First, CAPTURE’s modeling of poachers provides significant advances over previous models from behavioral game theory and conservation biology. This accounts for: (i) the defender’s imperfect detection of poaching signs; (ii) complex temporal dependencies in the poacher’s behaviors; (iii) lack of knowledge of numbers of poachers. Second, we provide two new heuristics: parameter separation and target abstraction to reduce the computational complexity in learning the poacher models. Third, we present a new game-theoretic algorithm for computing the defender’s optimal patrolling given the complex poacher model. Finally, we present detailed models and analysis of realworld poaching data collected over 12 years in Queen Elizabeth National Park in Uganda to evaluate our new model’s prediction accuracy. This paper thus presents the largest dataset of real-world defender-adversary interactions analyzed in the security games literature. CAPTURE will be tested in Uganda in early 2016.
2016_16_teamcore_wildlife_protection.pdf
Fei Fang, Thanh H. Nguyen, Rob Pickles, Wai Y. Lam, Gopalasamy R. Clements, Bo An, Amandeep Singh, Milind Tambe, and Andrew Lemieux. 2016. “Deploying PAWS: Field Optimization of the Protection Assistant for Wildlife Security.” In Twenty-Eighth Innovative Applications of Artificial Intelligence Conference.Abstract
Poaching is a serious threat to the conservation of key species and whole ecosystems. While conducting foot patrols is the most commonly used approach in many countries to prevent poaching, such patrols often do not make the best use of limited patrolling resources. To remedy this situation, prior work introduced a novel emerging application called PAWS (Protection Assistant for Wildlife Security); PAWS was proposed as a game-theoretic (“security games”) decision aid to optimize the use of patrolling resources. This paper reports on PAWS’s significant evolution from a proposed decision aid to a regularly deployed application, reporting on the lessons from the first tests in Africa in Spring 2014, through its continued evolution since then, to current regular use in Southeast Asia and plans for future worldwide deployment. In this process, we have worked closely with two NGOs (Panthera and Rimba) and incorporated extensive feedback from professional patrolling teams. We outline key technical advances that lead to PAWS’s regular deployment: (i) incorporating complex topographic features, e.g., ridgelines, in generating patrol routes; (ii) handling uncertainties in species distribution (game theoretic payoffs); (iii) ensuring scalability for patrolling large-scale conservation areas with fine-grained guidance; and (iv) handling complex patrol scheduling constraints.
2016_4_teamcore_iaai16_paws.pdf
Amulya Yadav, Ece Kamar, Barbara Grosz, and Milind Tambe. 2016. “HEALER: POMDP Planning for Scheduling Interventions among Homeless Youth (Demonstration).” In International conference on Autonomous Agents and Multiagent Systems.Abstract
Adaptive software agents like HEALER have been proposed in the literature recently to recommend intervention plans to homeless shelter officials. However, generating networks for HEALER’s input is challenging. Moreover, HEALER’s solutions are often counter-intuitive to people. This demo paper makes two contributions. First, we demonstrate HEALER’s Facebook application, which parses the Facebook contact lists in order to construct an approximate social network for HEALER. Second, we present a software interface to run human subject experiments (HSE) to understand human biases in recommendation of intervention plans. We plan to use data collected from these HSEs to build an explanation system for HEALER’s solutions.
2016_24_teamcore_aamasdemo_amulya.pdf
Amulya Yadav, Hau Chan, Albert Jiang, Eric Rice, Ece Kamar, Barbara Grosz, and Milind Tambe. 2016. “POMDPs for Assisting Homeless Shelters - Computational and Deployment Challenges.” In AAMAS 2016 IDEAS Workshop.Abstract
This paper looks at challenges faced during the ongoing deployment of HEALER, a POMDP based software agent that recommends sequential intervention plans for use by homeless shelters, who organize these interventions to raise awareness about HIV among homeless youth. HEALER’s sequential plans (built using knowledge of social networks of homeless youth) choose intervention participants strategically to maximize influence spread, while reasoning about uncertainties in the network. In order to compute its plans, HEALER (i) casts this influence maximization problem as a POMDP and solves it using a novel planner which scales up to previously unsolvable real-world sizes; (ii) and constructs social networks of homeless youth at low cost, using a Facebook application. HEALER is currently being deployed in the real world in collaboration with a homeless shelter. Initial feedback from the shelter officials has been positive but they were surprised by the solutions generated by HEALER as these solutions are very counterintuitive. Therefore, there is a need to justify HEALER’s solutions in a way that mirrors the officials’ intuition. In this paper, we report on progress made towards HEALER’s deployment and detail first steps taken to tackle the issue of explaining HEALER’s solutions.
2016_23_teamcore_ideas_amulya.pdf
Sara Mc Carthy, Milind Tambe, Christopher Kiekintveld, Meredith L. Gore, and Alex Killion. 2016. “Preventing Illegal Logging: Simultaneous Optimization of Resource Teams and Tactics for Security.” In AAAI conference on Artificial Intelligence (AAAI).Abstract
Green security – protection of forests, fish and wildlife – is a critical problem in environmental sustainability. We focus on the problem of optimizing the defense of forests against illegal logging, where often we are faced with the challenge of teaming up many different groups, from national police to forest guards to NGOs, each with differing capabilities and costs. This paper introduces a new, yet fundamental problem: Simultaneous Optimization of Resource Teams and Tactics (SORT). SORT contrasts with most previous game-theoretic research for green security – in particular based on security games – that has solely focused on optimizing patrolling tactics, without consideration of team formation or coordination. We develop new models and scalable algorithms to apply SORT towards illegal logging in large forest areas. We evaluate our methods on a variety of synthetic examples, as well as a real-world case study using data from our on-going collaboration in Madagascar.
12160-56367-1-pb.pdf
Leandro Soriano Marcolino, Aravind Lakshminarayanan, Amulya Yadav, and Milind Tambe. 2016. “Simultaneous Influencing and Mapping Social Networks (Extended Abstract).” In International Conference on Autonomous Agents and Multiagent Systems (AAMAS).Abstract
Influencing a social network is an important technique, with potential to positively impact society, as we can modify the behavior of a community. For example, we can increase the overall health of a population; Yadav et al. (2015) [4], for instance, spread information about HIV prevention in homeless populations. However, although influence maximization has been extensively studied [2, 1], their main motivation is viral marketing, and hence they assume that the social network graph is fully known, generally taken from some social media network. However, the graphs recorded in social media do not really represent all the people and all the connections of a population. Most critically, when performing interventions in real life, we deal with large degrees of lack of knowledge. Normally the social agencies have to perform several interviews in order to learn the social network graph [3]. These highly unknown networks, however, are exactly the ones we need to influence in order to have a positive impact in the real world, beyond product advertisement. Additionally, learning a social network graph is very valuable per se. Agencies need data about a population, in order to perform future actions to enhance their well-being, and better actuate in their practices [3]. As mentioned, however, the works in influence maximization are currently ignoring this problem. Each person in a social network actually knows other people, including the ones she cannot directly influence. When we select someone for an intervention (to spread influence), we also have an opportunity to obtain knowledge. Therefore, in this work we present for the first time the problem of simultaneously influencing and mapping a social network. We study the performance of the classical influence maximization algorithm in this context, and show that it can be arbitrarily low. Hence, we study a class of algorithms for this problem, performing an experimentation using four real life networks of homeless populations. We show that our algorithm is competitive with previous approaches in terms of influence, and is significantly better in terms of mapping.
2016_14_teamcore_aamas2016_i.pdf
Shahrzad Gholami, Bryan Wilder, Matthew Brown, Dana Thomas, Nicole Sintov, and Milind Tambe. 2016. “Toward Addressing Collusion among Human Adversaries in Security Games.” European Conference on Artificial Intelligence (ECAI )[short paper].Abstract
Security agencies including the US Coast Guard, the Federal Air Marshal Service and the Los Angeles Airport police are several major domains that have been deploying Stackelberg security games and related algorithms to protect against a single adversary or multiple, independent adversaries strategically. However, there are a variety of real-world security domains where adversaries may benefit from colluding in their actions against the defender. Given the potential negative effect of these collusive actions, the defender has an incentive to break up collusion by playing off the self-interest of individual adversaries. This paper deals with problem of collusive security games for rational and bounded rational adversaries. The theoretical results verified with human subject experiments showed that behavior model which optimizes against bounded rational adversaries provides demonstrably better performing defender strategies against human subjects.
2016_34_teamcore_sgholami_ecai16.pdf
Chao Zhang, Victor Bucarey, Ayan Mukhopadhyay, Arunesh Sinha, Yundi Qian, Yevgeniy Vorobeychik, and Milind Tambe. 2016. “Using abstractions to solve opportunistic crime security games at scale.” In International Conference on Autonomous Agents and Multiagent Systems (AAMAS).Abstract
In this paper, we aim to deter urban crime by recommending optimal police patrol strategies against opportunistic criminals in large scale urban problems. While previous work has tried to learn criminals’ behavior from real world data and generate patrol strategies against opportunistic crimes, it cannot scale up to large-scale urban problems. Our first contribution is a game abstraction framework that can handle opportunistic crimes in large-scale urban areas. In this game abstraction framework, we model the interaction between officers and opportunistic criminals as a game with discrete targets. By merging similar targets, we obtain an abstract game with fewer total targets. We use real world data to learn and plan against opportunistic criminals in this abstract game, and then propagate the results of this abstract game back to the original game. Our second contribution is the layer-generating algorithm used to merge targets as described in the framework above. This algorithm applies a mixed integer linear program (MILP) to merge similar and geographically neighboring targets in the large scale problem. As our third contribution, we propose a planning algorithm that recommends a mixed strategy against opportunistic criminals. Finally, our fourth contribution is a heuristic propagation model to handle the problem of limited data we occasionally encounter in largescale problems. As part of our collaboration with local police departments, we apply our model in two large scale urban problems: a university campus and a city. Our approach provides high prediction accuracy in the real datasets; furthermore, we project significant crime rate reduction using our planning strategy compared to current police strategy.
2016_11_teamcore_abstract_game.pdf
Amulya Yadav, Hau Chan, Albert Xin Jiang, Haifeng Xu, Eric Rice, and Milind Tambe. 2016. “Using Social Networks to Aid Homeless Shelters: Dynamic Influence Maximization under Uncertainty.” In International Conference on Autonomous Agents and Multiagent Systems (AAMAS) 2016.Abstract
This paper presents HEALER, a software agent that recommends sequential intervention plans for use by homeless shelters, who organize these interventions to raise awareness about HIV among homeless youth. HEALER’s sequential plans (built using knowledge of social networks of homeless youth) choose intervention participants strategically to maximize influence spread, while reasoning about uncertainties in the network. While previous work presents influence maximizing techniques to choose intervention participants, they do not address three real-world issues: (i) they completely fail to scale up to real-world sizes; (ii) they do not handle deviations in execution of intervention plans; (iii) constructing real-world social networks is an expensive process. HEALER handles these issues via four major contributions: (i) HEALER casts this influence maximization problem as a POMDP and solves it using a novel planner which scales up to previously unsolvable realworld sizes; (ii) HEALER allows shelter officials to modify its recommendations, and updates its future plans in a deviation-tolerant manner; (iii) HEALER constructs social networks of homeless youth at low cost, using a Facebook application. Finally, (iv) we show hardness results for the problem that HEALER solves. HEALER will be deployed in the real world in early Spring 2016 and is currently undergoing testing at a homeless shelter.
2016_10_teamcore_amulya_aamas16.pdf
2015
A. Sinha, T. H. Nguyen, D. Kar, M. Brown, M. Tambe, and A.X. Jiang. 11/17/2015. “From Physical Security to Cyber Security .” Journal of Cybersecurity.Abstract
Security is a critical concern around the world. In many domains from cybersecurity to sustainability, limited security resources prevent complete security coverage at all times. Instead, these limited resources must be scheduled (or allocated or deployed), while simultaneously taking into account the importance of different targets, the responses of the adversaries to the security posture, and the potential uncertainties in adversary payoffs and observations, etc. Computational game theory can help generate such security schedules. Indeed, casting the problem as a Stackelberg game, we have developed new algorithms that are now deployed over multiple years in multiple applications for scheduling of security resources. These applications are leading to realworld use-inspired research in the emerging research area of “security games.” The research challenges posed by these applications include scaling up security games to real-world-sized problems, handling multiple types of uncertainty, and dealing with bounded rationality of human adversaries. In cybersecurity domain, the interaction between the defender and adversary is quite complicated with high degree of incomplete information and uncertainty. While solutions have been proposed for parts of the problem space in cybersecurity, the need of the hour is a comprehensive understanding of the whole space including the interaction with the adversary. We highlight the innovations in security games that could be used to tackle the game problem in cybersecurity.
2015_40_teamcore_cybsec_tyv007_full.pdf
L. S. Marcolino. 1/2015. “Multi-agent Team Formation: Solving Complex Problems by Aggregating Opinions .” In Conference on Artificial Intelligence (AAAI 2015). (Doctoral Consortium). Texas, USA.Abstract
Aggregating the opinions of different agents is a powerful way to find high-quality solutions to complex problems. However, when using agents in this fashion, there are two fundamental open questions. First, given a universe of agents, how to quickly identify which ones should be used to form a team? Second, given a team of agents, what is the best way to aggregate their opinions? Many researchers value diversity when forming teams. LiCalzi and Surucu (2012) and Hong and Page (2004) propose models where the agents know the utility of the solutions, and the team converges to the best solution found by one of its members. Clearly in complex problems the utility of solutions would not be available, and agents would have to resort to other methods, such as voting, to take a common decision. Lamberson and Page (2012) study diversity in the context of forecasts, where the solutions are represented by real numbers and the team takes the average of the opinion of its members. Domains where the possible solutions are discrete, however, are not captured by such a model. I proposed a new model to study teams of agents that vote in discrete solution spaces (Marcolino, Jiang, and Tambe 2013), where I show that a diverse team of weaker agents can overcome a uniform team made of copies of the best agent. However, this phenomenon does not always occur, and it is still necessary to identify when we should use diverse teams and when uniform teams would be more appropriate. Hence, in Marcolino et al. (2014b), I shed a new light into this problem, by presenting a new, more general model of diversity for teams of voting agents. Using that model I can predict that diverse teams perform better than uniform teams in problems with a large action space. All my predictions are verified in a real system of voting agents, in the Computer Go domain. I show that: (i) a team of diverse players gets a higher winning rate than a uniform team made of copies of the best agent; (ii) the diverse team plays increasingly better as the board size increases. Moreover, I also performed an experimental study in the building design domain. This is a fundamental domain in the current scenario, since it is known that the design of a building has a major impact in the consumption of energy throughout its whole lifespan (Lin and Gerber 2014). It is fundamental to design energy efficient buildings. Meanwhile, it is important to balance other factors, such as construction cost, creating a multi-objective optimization problem. I show that by aggregating the opinions of a team of agents, a higher number of 1 st ranked solutions in the Pareto frontier is found than when using a single agent. Moreover, my approach eliminates falsely reported 1 st ranked solutions (Marcolino et al. 2014a; 2015). As mentioned, studying different aggregation rules is also fundamental. In Jiang et al. (2014), I introduce a novel method to extract a ranking from agents, based on the frequency that actions are played when sampling them multiple times. My method leads to significant improvements in the winning rate in Go games when using the Borda voting rule to aggregate the generated rankings.
2015_2_teamcore_aaai15.pdf
L. S. Marcolino, H. Xu, D. Gerber, B. Kolev, S. Price, E. Pantazis, and M. Tambe. 2015. “Agent Teams for Design Problems .” In International Workshop on Coordination, Organisations, Institutions and Norms (COIN 2015).Abstract
Design imposes a novel social choice problem: using a team of voting agents, maximize the number of optimal solutions; allowing a user to then take an aesthetical choice. In an open system of design agents, team formation is fundamental. We present the first model of agent teams for design. For maximum applicability, we envision agents that are queried for a single opinion, and multiple solutions are obtained by multiple iterations. We show that diverse teams composed of agents with different preferences maximize the number of optimal solutions, while uniform teams composed of multiple copies of the best agent are in general suboptimal. Our experiments study the model in bounded time; and we also study a real system, where agents vote to design buildings.
2015_31_teamcore_coin2015.pdf
L. S. Marcolino, D. Gerber, B. Kolev, S. Price, E. Pantazis, Y. Tian, and M. Tambe. 2015. “Agents vote for the environment: Designing energy-efficient architecture .” In Workshop on Computational Sustainability (AAAI 2015).Abstract
Saving energy is a major concern. Hence, it is fundamental to design and construct buildings that are energy-efficient. It is known that the early stage of architectural design has a significant impact on this matter. However, it is complex to create designs that are optimally energy efficient, and at the same time balance other essential criterias such as economics, space, and safety. One state-of-the art approach is to create parametric designs, and use a genetic algorithm to optimize across different objectives. We further improve this method, by aggregating the solutions of multiple agents. We evaluate diverse teams, composed by different agents; and uniform teams, composed by multiple copies of a single agent. We test our approach across three design cases of increasing complexity, and show that the diverse team provides a significantly larger percentage of optimal solutions than single agents.
2015_30_teamcore_wcs2015.pdf
Matthew Brown. 2015. “Balancing Tradeoffs in Security Games: Handling Defenders and Adversaries with Multiple Objectives ”.Abstract
Stackelberg security games (SSG) have received a significant amount of attention in the literature for modeling the strategic interactions between a defender and an adversary, in which the defender has a limited amount of security resources to protect a set of targets from a potential attack by the adversary. SSGs are at the heart of several significant decision-support applications deployed in real world security domains. All of these applications rely on standard assumptions made in SSGs, including that the defender and the adversary each have a single objective which is to maximize their expected utility. Given the successes and real world impact of previous SSG research, there is a natural desire to push towards increasingly complex security domains, leading to a point where considering only a single objective is no longer appropriate. My thesis focuses on incorporating multiple objectives into SSGs. With multiple conflicting objectives for either the defender or adversary, there is no one solution which maximizes all objectives simultaneously and tradeoffs between the objectives must be made. Thus, my thesis provides two main contributions by addressing the research challenges raised by considering SSGs with (1) multiple defender objectives and (2) multiple adversary objectives. These contributions consist of approaches for modeling, calculating, and analyzing the tradeoffs between objectives in a variety of different settings. First, I consider multiple defender objectives resulting from diverse adversary threats where protecting against each type of threat is treated as a separate objective for the defender. Second, I investigate the defender’s need to balance between the exploitation of collected data and the exploration of alternative strategies in patrolling domains. Third, I explore the necessary tradeoff between the efficacy and the efficiency of the defender’s strategy in screening domains. Forth, I examine multiple adversary objectives for heterogeneous populations of boundedly rational adversaries that no longer strictly maximize expected utility. The contributions of my thesis provide the novel game models and algorithmic techniques required to incorporate multiple objectives into SSGs. My research advances the state of the art in SSGs and opens up the model to new types of security domains that could not have been handled previously. As a result, I developed two applications for real world security domains that either have been or will be tested and evaluated in the field.
2015_23_teamcore_brown_thesis.pdf
Benjamin Ford, Thanh Nguyen, Milind Tambe, Nicole Sintov, and Francesco Delle Fave. 2015. “Beware the Soothsayer: From Attack Prediction Accuracy to Predictive Reliability in Security Games .” In Conference on Decision and Game Theory for Security.Abstract
. Interdicting the flow of illegal goods (such as drugs and ivory) is a major security concern for many countries. The massive scale of these networks, however, forces defenders to make judicious use of their limited resources. While existing solutions model this problem as a Network Security Game (NSG), they do not consider humans’ bounded rationality. Previous human behavior modeling works in Security Games, however, make use of large training datasets that are unrealistic in real-world situations; the ability to effectively test many models is constrained by the time-consuming and complex nature of field deployments. In addition, there is an implicit assumption in these works that a model’s prediction accuracy strongly correlates with the performance of its corresponding defender strategy (referred to as predictive reliability). If the assumption of predictive reliability does not hold, then this could lead to substantial losses for the defender. In the following paper, we (1) first demonstrate that predictive reliability is indeed strong for previous Stackelberg Security Game experiments. We also run our own set of human subject experiments in such a way that models are restricted to learning on dataset sizes representative of real-world constraints. In the analysis on that data, we demonstrate that (2) predictive reliability is extremely weak for NSGs. Following that discovery, however, we identify (3) key factors that influence predictive reliability results: the training set’s exposed attack surface and graph structure.
2015_36_teamcore_ford15_gamesec.pdf

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