The Internet of Things (IoT) revolution is expected to drive change in our society in an unprecedented way. It will help us collect exponentially more data in a continuous manner and get deeper insights derived from such data. There are several surveys done in the area of IoT in terms of enabling technologies, application domains, applications, protocols, and open issues. Among the open issues discussed are important concerns such as security and privacy. The low capabilities of IoT devices in terms of their energy and computing capabilities, the unreliable nature of the wireless channel, and physical vulnerability are among the contributing factors to some unique security vulnerabilities. This chapter summarizes recent research results in the area of IoT security. It emphasizes the challenges of privacy and security in IoT. The discussion considers open challenges in security and data privacy such as (1) scale and constrained network elements, (2) privacy in data collection as well as data sharing and management, and (3) identity management and authentication. The chapter presents existing literature, a critical assessment of the work that has been done, develops a perspective on the area, and evaluates trends. It also presents taxonomy of IoT security risks, attacks, and mechanisms. © 2016 Elsevier Inc. All rights reserved.