How Miley Cyrus Was Hacked

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."