Mark T. Abene (born February 23, 1972) is an American infosec expert and entrepreneur, originally from New York City. Better known by his pseudonym Phiber Optik, he was once a member of the hacker groups Legion of Doom and Masters of Deception. Phiber Optik was a high-profile hacker in the 1980s and early 1990s, appearing in The New York Times, Harper's, Esquire, in debates and on television. He is an important figure in the 1995 non-fiction book, Masters of Deception — The Gang that Ruled Cyberspace (ISBN 978-0-06-092694-6).