In June, the secure Signal account of a European foreign minister pinged with a text message. The sender claimed to be U.S. Secretary of State Marco Rubio with an urgent request. A short time later, two other foreign ministers, a U.S. governor, and a member of Congress received the same message, this time accompanied by a sophisticated voice memo impersonating Rubio. Although the communication appeared to be authentic, its tone matching what would be expected from a senior official, it was