Malicious Cyber Operations, “Hackbacks” and International Law: An Austrian Example as a Basis for Discussion on Permissible Responses

In January 2020, Austria publicly announced that some of its governmental institutions have been hit by a significant malicious cyber operation and that it cannot be denied – at least for the moment – that a state was behind this operation. One month later, the Austrian Foreign Ministry declared the cyber operation to be officially over. While Austria noted that it took “countermeasures” against the operation, it is not entirely clear what it meant by that. This article elaborates the question what response options a state like Austria would have against a malicious cyber operation under the current framework of international law. It, hence, tries to answer when a “hackback” is lawful under international law and when it is not.