In today's communication systems, the most damaging security threats are not originating from the outsiders but from the trusted insiders - both malicious insiders and negligent insiders. Always endowed with high privileges, insiders are significantly prone to conduct acts that can cause catastrophic damages to the whole system either intentionally or unintentionally. Characterised by the full and rapid integration of information and communication technologies, smart grid - arguably the largest national critical engineering infrastructure - is suffering from a multitude of security threats initiated from both outsiders and insiders. Without security guarantee, the promising benefits of achieving an efficient, green, and reliable power grid would not be a success. In this study, the authors investigate the insider threats and summarise the existing threats detection solutions in smart grid communication systems. In addition, a novel hybrid insider threats modelling, analysis, and detection framework, which is based on stochastic Petri net and behaviour rule specifications, is proposed to contain insider threats in smart grid communication systems.