Cyber-warfare is no longer science fiction. It is quite real. With global infrastructure growing increasingly dependent on cyberspace and its networking systems, defense against cyber-attacks is already a worldwide concern. Unimaginable 20 years ago, states dependent on the networked world are trying to come to a consensus on the regulation of cyberspace. International law regulation of cyberspace is one of the key issues. Can states use force in response to cyber-attacks? Can a cyber-attack be so serious that it can trigger self-defense mechanisms via international law? Is it possible that future cyber-attacks could erupt into full scale physical wars? What are states’ current attitudes towards cyber-warfare norms in international law? This article will illuminate these issues and several other important questions, analyze key aspects of international legal regulation of cyberspace and cyber-warfare, and present conclusions.