Miley Cyrus Hacker -- Secrets Revealed

A man who claims to have hacked the emails and cell phones of numerous celebrities -- including those who were hacked by the Hackerazzi who now faces criminal charges -- has given TMZ a road map on how he did the dirty deed.

A man who has been contacting TMZ for nearly two years -- trying to peddle multiple celeb images, including nude pics of Scarlett Johansson -- has revealed how he hacked Miley Cyrus' Gmail account.

The man says he simply went to Miley's Gmail and tried accessing it. The prompt asked a security question ... the name of one of her girlfriends. He guessed the one she's known the longest, based on a Google search -- and he scored.

He says, "When I saw that, I couldn't believe it."

As for who the man is ... we've never met him, but it could be Christoper Chaney using a different email address.