The emerging Internet of Things (IoT) is unleashing the next wave of innovations due to its inherent capability of connecting billions of devices together, which bridges the gap between the physical world and cyber world. In recent years, the successful applications of IoT have demonstrated the massive potential benefits that IoT can make for global social economy. Coming along with the benefits, the IoT is facing an increasingly number of security and privacy challenges, including data encryption, privacy, secure machine-to-machine (M2M) communications, device security, cyber-attack, cloud security in IoT environment, and more. These challenges must be fixed quickly and effectively. To address these challenges, this special issue was proposed to bring recent research progress in theories and applications in privacy, data assurance, security issues in IoT that may help put together a clear picture for the security of IoT.