Umbuk,[1] trik konfidensi atau trik kepercayaan adalah upaya untuk melakukan penipuan setelah mendapatkan kepercayaan korban terlebih dahulu. Trik konfidensi mengeksploitasi korban menggunakan sifat mudah percaya, kenaifan, belas kasih, kesombongan, kepercayaan diri, tidak bertanggung jawab, dan keserakahan. Para peneliti telah mendefinisikan trik konfidensi sebagai "ciri khas dari perilaku penipuan [...] yang bertujuan melakukan pertukaran sukarela tetapi sebenarnya tidak saling menguntungkan", karena mereka "menguntungkan penipu dengan mengorbankan korban mereka.[2]Orang yang melakukan pengumbukan disebut pengumbuk (scammer).
- Bell, J. Bowyer; Whaley, Barton (1982). Cheating and Deception (reprint 1991). Transaction Publishers. ISBN 978-0887388682.
- Blundell, Nigel (1984) [1982]. The World's Greatest Crooks and Conmen and other mischievous malefactors. Octopus Books. ISBN 978-0706421446.
- Dillon, Eamon (2008) [2008]. The Fraudsters: Sharks and Charlatans – How Con Artists Make Their Money. Merlin Publishing. ISBN 978-1903582824.
- Ford, Charles V. (1999) [1999]. Lies! Lies!! Lies!!!: The Psychology of Deceit. American Psychiatric. ISBN 978-0880489973.
- Henderson, Les (2000). Crimes of Persuasion: Schemes, scams, frauds. Coyote Ridge. ISBN 978-0968713303.
- Kaminski, Marek M. (2004). Games Prisoners Play. Princeton: Princeton University Press. ISBN 978-0691117218.
- Konnikova, Maria (2016). The Confidence Game: Why We Fall for It...Every Time. ISBN 978-0525427414.
- Lazaroff, Steven & Rodger, Mark (2018) [2018]. History's Greatest Deceptions and Confidence scams. Rodger & Laz Publishing S.E.N.C. ISBN 978-1775292128.
- Maurer, David W. (1999) [1940]. The Big Con: The Story of the Confidence Man and the Confidence Game. Bobbs Merrill / Anchor Books. ISBN 978-0385495387.
- Maurer, David W. (1974). The American Confidence Man. Springfield: Charles C. Thomas, Publisher. ISBN 978-0398029746.
- Reading, Amy (2012). The Mark Inside: A Perfect Swindle, a Cunning Revenge, and a Small History of the Big Con. Knopf. ISBN 978-0307473592.
- Smith, Jeff (2009). Soapy Smith: The Life and Death of a Scoundrel. Juneau: Klondike Research. ISBN 978-0981974309.
- Sutherland, Edwin Hardin (1937). The Professional Thief (reprint 1989). University of Chicago Press. ISBN 978-0226780511.
- Weil, J.R. "Yellow Kid" (1948) [2004]. Con Man: A Master Swindler's Own Story. Broadway Books. ISBN 978-0767917377.
- Zhang, Yingyu (2017). The Book of Swindles: Selections from a Late Ming Collection. Columbia University Press. ISBN 978-0231178631.