Offensive cyber capabilities run the gamut from sophisticated, long-term disruptions of physical infrastructure to malware used to target human rights journalists. As these capabilities continue to proliferate with increasing complexity and to new types of actors, the imperative to slow and counter their spread only strengthens. But to confront this growing menace, practitioners and policy makers must understand the processes and incentives behind it. The issue of cyber capability proliferation has often been presented as attempted export controls on intrusion software, creating a singular emphasis on malware components. This primer reframes the narrative of cyber capability proliferation to be more in line with the life cycle of cyber operations as a whole, presenting five pillars of offensive cyber capability: vulnerability research and exploit development, malware payload generation, technical command and control, operational management, and training and support. The primer describes how governments, criminal groups, industry, and Access-as-a-Service (AaaS) providers work within either self-regulated or semi-regulated markets to proliferate offensive cyber capabilities and suggests that the five pillars give policy makers a more granular framework within which to craft technically feasible counterproliferation policies without harming valuable elements of the cybersecurity industry. These recommended policies are developed in more detail, alongside three case studies of AaaS firms, in our companion report, Countering Cyber Proliferation: Zeroing in on Access as a Service.