The Internet of Things (IoT) is completely revolutionizing our society because of its potential to connect a broad spectrum of devices globally to the internet. The IoT has brought the real power of the internet, data processing and analytics to the physical objects in our environment, with a plethora of smart and intelligent IoT devices. It has been estimated that by 2021, nearly one billion IoT devices will be purchased and installed every hour, with significant social, technological, and commercial effects on our lives. However, the widespread demand for IoT devices makes them attractive targets for attackers performing malicious activities. Extensive efforts have been made to address various security and privacy issues. This chapter presents in detail various security issues and potential attacks on IoT devices, with their solution and classification.