Privacy, security, and the dynamics of networked information sharing

This thesis explores coordination of decentralized information systems in three independent essays. Each essay addresses a significant policy issue by examining how information is shared in a decentralized environment, and the challenges of coordinating that information flow.;The first essay argues that internet users lack the information and incentives to adequately secure themselves. The essay shows that social networks are uniquely suited to create contextual information about security threats, and can share useful security information inside trusted networks of social ties without compromising privacy or introducing new risks. Two systems that rely on social networks to patch vulnerable operating systems and avoid dangerous websites are proposed and analyzed.;The second essay presents a study of recent privacy policies that force companies to disclose data breaches exposing personal information. Taking advantage of the subsequent increase in publicly-announced breaches, an event study analysis shows a significant negative impact on the share price of the companies involved.;The third essay examines collaborative problem-solving situations in which only one individual needs to find a good solution to provide a social benefit. The motivating example is the growing phenomenon of crowdsourcing, in which a group of problem solvers competes to find the best answer to a difficult question. Results of an agent-based model demonstrate the limits of collaboration and challenge what assumptions must be made about the problem and the problem solvers to yield the benefits of information sharing. The impact of different network structures is also explored.;Beyond the specific research question, each chapter yields lessons applicable to larger policy issues. The security implications of social network tools can guide policies on privacy, identity tools and incentive-based information security measures. The study of data breaches also informs the broader efficacy of transparency as a tool for reducing bad behavior and encouraging good behavior among actors in a larger market. Modeling the new phenomenon of crowdsourcing enables a better understanding of the classes of group problem solving, and articulates how to promote innovation and avoid pitfalls in collaboration. The essays conclude with a discussion of the importance of studying the context of information sharing.