William Landreth (born 1964) is an American hacker notable for his cracking activities during the early 1980s within an exclusive cracking club called "The Inner Circle", and subsequent 1986 disappearance (from which he re-appeared a year later). His book Out of the Inner Circle: A Hacker's Guide to Computer Security, published in 1986, is considered a best-seller.
- Out of the Inner Circle: A Hacker's Guide to Computer Security (Microsoft Press, 1985) ISBN 0-914845-36-5
- "A Hacker Vanishes Computer Whiz, Missing Since September, a Source of Mystery". Los Angeles Times. December 11, 1986. Retrieved February 3, 2011.
- "Hacker Is Down And Out In San Diego". Sydney Morning Herald. April 3, 1989. Retrieved February 3, 2011.
- "Bill Landreth: The Cracker & Out Of The Inner Circle & Pig Sty". September 26, 2011. Retrieved April 9, 2013.[permanent dead link]