The rapid growth of technology and the increasing dependence on digital infrastructure have turned the concept of state responsibility in cyberspace into one of the most pressing challenges of the contemporary international order. The absence of a unified definition of “cyber aggression” and clear attribution standards has enabled states to operate in the gray zone between peace and conflict, conducting costly operations without direct accountability. This study, using an explanatory–analytical approach and a qualitative comparative method, analyzes international documents, security reports, and state behaviors to propose a three-layered framework: “norms and international law,” “multilayered deterrence and defense,” and “credible attribution with transparent narrative-building.” Findings reveal that weak legal mechanisms and a lack of intelligence cooperation undermine the legitimacy of state responses and increase the risk of civilian harm. Conversely, the combination of technical cooperation, active norm-building, and enhanced transparency can create sustainable deterrence. The study concludes that strengthening technical collaboration, improving attribution transparency, and enhancing the role of international institutions are essential for accountability and civilian protection.