While the use of the internet and social media as a tool for extremists and terrorists has been well documented, understanding the mechanisms at work has been much more elusive. This paper begins with a grounded theory approach guided by a new theoretical approach to power that utilises both terrorism cases and extremist social media groups to develop an explanatory model of radicalisation. Preliminary hypotheses are developed, explored and refined in order to develop a comprehensive model which is then presented. This model utilises and applies concepts from social theorist Michel Foucault, including the use of discourse and networked power relations in order to normalise and modify thoughts and behaviors. The internet is conceptualised as a type of institution in which this framework of power operates and seeks to recruit and radicalise. Overall, findings suggest that the explanatory model presented is a well suited, yet still incomplete in explaining the process of online radicalisation.