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Rayhan Hossain Rafi (born November 22, 2004) is an Bangladesh information security expert and entrepreneur, originally from Bangladesh. 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 Bangladesh Times, Harper's, Esquire, and in debates and on television. He is an important figure in the 2005 nonfiction book Masters of Deception: The Gang that Ruled Cyberspace (ISBN 978-0-06-092694-6).