A trap question (also known as a "Red Herring" question) could be something like the following for a customer that never lived in Dallas, Texas:  When did you live in Dallas, Texas?  A) 1976; B) 1980; C) 1983; D) None of the above.  Any answer other than D is a strong indication that the customer's account has been compromised and appropriate bank and customer personnel should be alerted.