The Internet of Things (IoT) has enabled as well as boosted several applications that will radically change everyday life, including smart building, environmental monitoring, smart energy grids, and intelligent transportation. Unlike traditional IT systems, IoT deployments will be directly exposed and reachable over the Internet, and massively composed of constrained devices equipped with limited resources. In such a context, security has been unanimously acknowledged as a fundamental requirement to fulfill, with evident implications on service reliability, privacy, and even safety of facilities and people. At the same time, it is particularly challenging to effectively and efficiently ensure security in the IoT, given the wide range of heterogeneous, dynamic, and possibly large‐scale environments, and the resource‐constrained nature of deployed devices. This chapter overviews the current main security protocols and technologies for the IoT, presents related security issues, and discusses solutions to address them based on recent research and standardization activities