“It might also be used to reveal the public IP address of someone running [dark web browser] Tor somewhere.

Asked whether Athens/Hyena could be used to track government officials or other persons of interest to hostile groups, Mr Sullivan replied: “It depends what kind of tools they have to get it on the machine - physical access as opposed to remote access.

He added: “The bigger concern for them, because this involves human intel, is that now that this has been leaked the people who might still have this on their computers will be able to find it, and they might be able to find out who the asset is working for the CIA.