Earlier this month, the book industry website Publishers Marketplace announced that Little, Brown would be publishing “Re-Entry,” a novel by James Hannaham about a transgender woman paroled from a men’s prison. The book would be edited by Ben George.

Two days later, Mr. Hannaham got an email from Mr. George, asking him to send the latest draft of his manuscript. The email came to an address on Mr. Hannaham’s website that he rarely uses, so he opened up his usual account, attached the document, typed in Mr. George’s email address and a little note, and hit send.

“Then Ben called me,” Mr. Hannaham said, “to say, ‘That wasn’t me.’”

Mr. Hannaham was just one of countless targets in a mysterious international phishing scam that has been tricking writers, editors, agents and anyone in their orbit into sharing unpublished book manuscripts. It isn’t clear who the thief or thieves are, or even how they might profit from the scheme. High-profile authors like Margaret Atwood and Ian McEwan have been targeted, along with celebrities like Ethan Hawke. But short story collections and works by little-known debut writers have been attacked as well, even though they would have no obvious value on the black market.

In fact, the manuscripts do not appear to wind up on the black market at all, or anywhere on the dark web, and no ransoms have been demanded. When copies of the manuscripts get out, they just seem to vanish. So why is this happening?