An ongoing debate in the study of cyber warfare is the relative balance between the attacker and the defender in cyberspace. In this paper, the author advances the hypothesis that, with the right investments in people, process, and technology, proliferated and advanced artificial intelligence (AI) could ultimately advantage cyber defense. He explores how advanced AI is likely to fundamentally reshape the economics of cybersecurity and examines what it will take to realize the promise of a defense-dominant cyber environment. He further hypothesizes that advanced and proliferated AI will disrupt the economics of cyber in a profound way that advantages the defender―but only if action is taken to do so.