In this article, we show how Annemarie Mol’s notion of ontological politics helps to open up the research agenda for cyber security in Critical Security Studies. The article hence seeks to further the debate about STS and Critical Security Studies. The articles main claim is that the concept of ontological politics enables an engagement with the complex and transformative dynamics of ICT and the new security actors and practices that shape security politics in the digital age. By examining the virulent attacks executed by the Mirai botnet – one of the world’s largest, fiercest and most enduring botnets – we point to four aspects of cyber security that attention to the ontological politics of cyber security attunes us to: the proliferation and entanglement of security agencies, actors, sites and spaces. These aspects of cyber security, we argue, are becoming increasingly prominent alongside the development of the Internet of Things (IoT) and 5G-network technology. In conclusion, we discuss the wider security theoretical and normative-democratic implications of an engagement with the ontological politics of security by exploring three avenues for additional conversation between ontological politics and Critical Security Studies.