Legality of right of self-defense against cyber-attacks

With the rise of technological and digital advancements, cyberattacks have emerged in our lives as a serious threat, both to individuals and the private sector. However, the risks are even greater when the target are states. States often hold some of the most sensitive and valuable information, making them frequent targets of cyber operations. Attacks against national cyber infrastructure, defense systems, and intelligence networks put public safety, economic stability, and even state sovereignty at risk. As dependency on digital systems increases, so too do the legal and strategic challenges. Cyber operations have challenged traditional international law, particularly in terms of the use of force and the right to self-defense. Compared to conventional attacks, cyberattacks are harder to detect, attribute, and evaluate in terms of the scale and intensity required under legal frameworks such as the UN Charter. While many cyber incidents fall below the threshold of armed conflict, they are still capable of causing significant harm. This creates a legal grey area: can computer network attacks justify a state's right to self-defense under Article 51 of the UN Charter? This thesis explores whether states can legally invoke their right to self-defense in response to cyberattacks and, if so, under what conditions such attacks would trigger Article 51. The research begins by examining the foundations of traditional international law regarding the use of force and then analyzes how these principles apply in the cyber context. This includes both doctrinal legal analysis and the study of case examples. The thesis argues that cyberattacks can qualify as armed attacks, but only in exceptional cases, especially when their effects are comparable to those of kinetic force. However, issues such as sovereignty, attribution, and proportionality significantly complicate the lawful exercise of self-defense. Despite these challenges, international law still provides a guiding framework that can help regulate and legitimize state responses in cyberspace.