The key findings of this report are; 1) Active Cyber defence has significant potential in helping improve UK national cybersecurity 2) Active Cyber defence can play a powerful role in shaping the cybersecurity marketplace and furthering the interests of UK internet users and consumers 3) Active Cyber defense is a potentially useful model for export to like-minded countries 4) Active Cyber defense may constitute an emergent public good 5)Active cyber defense is not perfect, nor should we expect it to be.