Attribution of cyberattacks requires identifying those responsible for bad acts, prominently including states, and accurate attribution is a crucial predicate in contexts as diverse as criminal indictments, insurance coverage disputes, and cyberwar. But the difficult technical side of attribution is just the precursor to highly contested legal and policy questions about when and how to accuse governments of responsibility for cyberattacks. Although politics may largely determine whether attributions are made public, this Article argues that when cyberattacks are publicly attributed to states, such attributions should be governed by legal standards.
Instead of blocking the development of evidentiary standards for attribution, as the United States, France, the Netherlands, and the United Kingdom are currently doing, states should establish an international law requirement that public attributions must include sufficient evidence to enable crosschecking or corroboration of the accusations. This functionally-defined standard harnesses both governmental and nongovernmental attribution capabilities to shed light on states’ activities in cyberspace, and understanding state practice is a necessary precondition to establishing norms and customary international law to govern state behavior. Moreover, setting a clear evidentiary standard for cyberattack attribution has the potential to clarify currently unsettled general international law rules on evidence.
This Article also engages debates about institutional design for attributing cyberattacks. Companies and think tanks have made several recent proposals for the creation of an international entity that would handle attribution of state-sponsored cyberattacks. Although these proposals have much to recommend them, this Article argues that such an entity should supplement, not replace, the current decentralized system of attribution. Having a multiplicity of attributors—both governmental and nongovernmental—yields a greater likelihood that public attributions will serve the goals that attributors aim to achieve, namely, strengthening defenses, deterring attacks, and improving stability in and avoiding conflict over cyberspace.