response --- Good question @Bennette! Probably it depends on the details. As they say the devil is in the details. I don't see the exact example as an act of war, but, maybe as an illegal act - similar to conventional espionage. Maybe in such case if there is evidence who was the attacking agent the attacked country can prosecute it and seek extradition of the offender (as it is mentioned in this module - US has convicted Russian individuals).

Source author: Vladimir Nikolov vladimir984@yahoo.com