This chapter analyses the application of jus contra bellum(the law against war) to cyber operations and demonstrates that the vast majority of cyber operations fall below the threshold required for the application of jus contra bellum. It analyses whether cyber operations may reach and cross the three thresholds of jus contra bellum – namely a use of force, a threat of force and an armed attack. It has been observed that no State or international organisation has ever publicly and unequivocally qualified a cyber operation as a use of force, and a fortiori an armed attack. This chapter, however, demonstrates that in some circumstances cyber operations may amount to a use of force, a threat of force or even an armed attack. The conclusion is that most state-sponsored cyber operations fall short of the required thresholds. Hence, they should be considered beyond the legal framework of jus contra bellum.