This document discusses security issues in Internet of Things (IoT). It begins with an introduction to IoT, explaining how IoT works and its key features such as connectivity, analytics, integration and artificial intelligence. It then discusses security layers in IoT, including perception, network, application and support layers. It outlines common security threats at each layer like eavesdropping, denial of service attacks, and malware. The document also covers IoT security challenges, advantages and disadvantages of IoT.