ABSTRACT – On 3 February 2023, many States were victims of cyberattacks perpetrated by non-state actors. A few days later, NATO websites were attacked by the hacker group Killnet. On 13 February 2023, Italy was attacked by the hacker group NoName057. These examples show the frequency of cyberattacks on the global stage. As far as the Security Council is not enabled to intervene, if an armed cyberattack occurs, States can individually react, using the classic tool of international law: the inherent right of self-defence. Moreover, NATO and EU Treaties provide collective self-defence clauses, to guarantee the protection of the Member States. This paper aims to discuss the complex subject of cyberattacks, focusing on the different types of national and collective reactions. More in-depth, the analysis will be centred on articles 42 TEU and 222 TFEU which establish different instruments of cooperation between the Member States. These mechanisms could play a critical role in the European defence from cyberattacks .
