Market concentration affects each component of the cybersecurity risk equation (i.e. threat, vulnerability and impact). As the Internet ecosystem becomes more concentrated across a number of vectors from users and incoming links to economic market share, the locus of cyber risk moves towards these major hubs and the volume of systemic cyber risk increases. Mitigating cyber risk requires better measurement, diversity of systems, software and firms, attention to market concentration in cyber insurance pricing, and the deliberate choice to avoid ubiquitous interconnection in critical systems.