In 2018 Sandia National Laboratories launched the Civilian Cyber Strategic Initiative, an ongoing multi-year effort to characterize future threats to civilian cyber infrastructures, to inform research and development efforts to detect, attribute, counter, and recover from cyber attacks, and to inform program and capability investment decisions across the Energy and Homeland Security portfolio at Sandia. One of the primary objectives of the Civilian Cyber Strategic initiative is to leverage Sandia's systems analysis capabilities to characterize future threats and to support a new theory of deterrence. Towards the goal of supporting a new theory of deterrence in cyberspace, the purpose of this study was to understand how new and existing deterrence paradigms can be applied to cyberspace, to identify unique challenges and pitfalls associated with deterring adversaries in cyberspace, and to develop preliminary ideas for how our ability to deter cyber adversaries might be improved. Our approach combined literature reviews of relevant policy documents and the academic literature with interviews of experts both at Sandia and beyond.