When science fiction writers first imagined robot invasions, the idea was that bots would become smart and powerful enough to take over the world by force, whether on their own or as directed by some evildoer. In reality, something only slightly less scary is happening. Robots are getting better, every day, at impersonating humans. When directed by opportunists, malefactors and sometimes even nation-states, they pose a particular threat to democratic societies, which are premised on being open to the people.