The Internet of Things (IoT) acts as a tremendous network that is constructed by fusing diverse sensors. IoT can achieve the interconnection of individuals, things, and machines at any place and time and improve the function performance of network applications. However, the security of IoT has always been a major problem that may limit the application perspective of IoT technologies. Nowadays, industrial IOT (IIoT), Internet of vehicles (IoV), and smart home have become the three primary emerging perspectives of the current IoT studies, and it is necessary to systematically highlight the security analysis of these three types of scenarios. Hence, in this paper, guided by the three major IoT application scenarios, i.e., IIoT, IoV, and smart home, we sum up the development status of IoT security technologies, analyzed corresponding technical difficulties, and discussed several future outlook of challenges and development trends for the IoT technology.