Notable People & Occassions
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-Frank Abagnale: Successfully pretended to be over 8 different professions, including a doctor, a pilot and a lawyer.[1]
-Badir Brothers: 3 blind brothers who managed to successfully infiltrate the phone systems of telecom company Bezeq by pretending to be engineers and then asking company employees for passwords. [2]
-Defcon: Successfully infiltrated Fortune 500 companies, often with a mere phone call. [3]

Frank Abagnale was one of the most renowned impostors in history; he inspired the Hollywood film Catch Me if You Can
[2] http://www.wired.com/wired/archive/12.02/phreaks_pr.html
[3] http://money.cnn.com/2012/08/07/technology/walmart-hack-defcon