Secret services work in secret, but their agents sometimes leave traces. It’s not always as spectacular as in the case of the alleged spy balloon that American fighter jets took out of the sky over the Atlantic. The Australian author Alex Joske traces the more inconspicuous tracks.

WORLD: In your book you exposed agents of the Chinese Ministry of State Security (MSS). How did you do it?

Alex Joske: Very little of the information available online directly connects anyone to the MSS. I focused on identifying the different identities and the different forms of disguise that MSS officers use when dealing with aliens. And I saw the patterns behind the camouflage. For example, I noticed…