In Sherlock, what is the name of Moriarty’s criminal alias?

In Sherlock, Moriarty’s criminal alias is Richard Brook.

In series 3, Moriarty’s supporters and media representatives claim that the criminal mastermind was actually an innocent actor named Richard Brook. The story is designed to undermine Sherlock’s account of Moriarty and make Holmes appear to have invented his greatest enemy.

“Richard Brook” is a constructed identity rather than the name of a separate person. Moriarty uses the alias as part of a wider campaign to discredit Sherlock after his apparent death. The name also creates a public version of events that conflicts with what Sherlock and John know.

Viewers sometimes answer Jim Moriarty because that is Moriarty’s real name in the series. “Richard Brook” is specifically the alias introduced in “The Empty Hearse” and discussed during the attempt to prove that Moriarty never existed as a criminal mastermind.