In the past, home automation was a small market for technology enthusiasts. Interconnectivity between devices was down to the owner's technical skills and creativity, while security was non-existent or primitive, because cyber threats were also largely non-existent or primitive. This is not the case any more. The adoption of Internet of Things technologies, cloud computing, artificial intelligence and an increasingly wide range of sensing and actuation capabilities has led to smart homes that are more practical, but also genuinely attractive targets for cyber attacks. Here, we classify applicable cyber threats according to a novel taxonomy, focusing not only on the attack vectors that can be used, but also the potential impact on the systems and ultimately on the occupants and their domestic life. Utilising the taxonomy, we classify twenty five different smart home attacks, providing further examples of legitimate, yet vulnerable smart home configurations which can lead to second-order attack vectors. We then review existing smart home defence mechanisms and discuss open research problems. Reference Key security properties Vulnerabilities/challenges Security recommended Open problems identified Komninos et al. [1] Confidentiality Connected to Internet Auto-immunity to threats Resilience Physical tampering Reliability, availability Lin et al. [2] Confidentiality Phys./netw. accessibility Gateway architecture Auto-configuration Authentication Constrained resources Updates Access control Heterogeneity Nawir et al. [6] Smart meter integrity Remote connectivity Techn. countermeasures Standardisation Privacy Physical tampering Regulatory initiatives Impact evaluation, metrics Non-repudiation Malicious actuation Intrusion detection Authorisation Logging for audit/forensics Ziegeldorf et al.[5]