The rapid development and wide application of the Internet of Things (IoT) and sensor technologies have produced good opportunities for the development of IoT-based smart home systems (SHSs). However, during the rapid market expansion of SHSs, security challenges associated with SHSs have become a primary concern of people because they are so closely related to people's daily lives. These security problems may damage information assets and pose a serious threat to people's health and life. This study investigates security issues in SHSs and provides a comprehensive overview of research to date. In this review, after analyzing the existing definition and concept of SHSs proposed by authoritative encyclopedias and academic literature, we propose a more accurate, elaborated definition of SHSs, analyze their architecture, extract six natural and contextual features, and summarize spears (cyber-attack means) vs. shields (countermeasures) in detail in the context of SHSs. Then, the security frameworks and evaluation technologies in SHSs are discussed. Different scenarios for technology integration and the practical research results in SHSs, such as blockchain, cloud computing, Internet of Vehicles, and AI are presented meticulously. After that, two special issues related to security are discussed. We believe that future research on SHS security should focus on four aspects: the unification of architecture, resource limitation, fragmentation, and code and firmware security. In addition, research on SHS security should be given priority over its commercialization process.