Computer security is a field that is fundamentally co-dependent — an interplay between the potential risk created by technology and the actual threats created by adversaries. The dance between defenders, technologists and attackers is one that is rich and dynamic and fuels both a large active research community and a multi-billion dollar computer security industry. Inevitably, ethical issues are exposed at multiple levels of this stack—frequently at precisely those points where consequences are not well understood. Stefan Savage, PhD, Professor of Computer Science and Engineering at the University of California, San Diego, describes some of the ethical issues he has encountered in his work—ranging from measurement studies of cybercrime to identifying security vulnerabilities in automobiles—and explore how these issues have challenged and focused him.