Responding to malicious cyber operations: State countermeasures


With malicious cyber operations increasingly launched from one country to another, states are looking for effective ways to respond consistently with international law. Governments regularly resort to unfriendly but lawful acts of retorsion in the cyber context, such as the US expelling diplomats and imposing sanctions following the Solar Winds hack. International law also allows states to take `countermeasures? in response to wrongful acts in cyberspace and beyond.

Countermeasures are responses that would normally be unlawful but are justified when taken to stop and/or repair acts that violate international law. The use of countermeasures in cyberspace is marred by uncertainty and significant debates about the exact conditions for taking those measures. This includes controversies about how those conditions apply in the cyber context ? a challenge compounded by the speed, scale and covertness of cyber operations.

This discussion will explore the application of the international law on countermeasures in the cyber context, and its implications for response options to malicious cyber operations. It will also launch a research paper on `Countermeasures in cyberspace? by Chatham House?s International Law Programme.
This event will be hosted on 23 May 2024 - 5:00pm to 6:30pm UK time at Chatham House and online. To register your attendance, please register online or email

Date and Location

Thursday, May 23, 2024 - 12:00pm to 1:30pm
Chatham House
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10 St James's Square
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