ShinBeth

From 911Encyclopedia:

Israeli counter-intelligence and internal security service, who is believed to have three operational departments and five support departments. The Arab Affairs Department, known as Henza is believed of having observed some Hamas-related suspects in the Boston Area during 2001. Another group was maybe responsible for observing the muslim students at the flight school and reporting to the Mossad, who then warned the United States twice on a possible attack and informed the MI6, too. There is a speculation around, that Daniel Lewin (Flight 11 ->) was working for ShinBeth, observing other hijackers, without knowing of being a victim of an attack. Actually in an early FAA report (->), he was even shot on that flight. (->early warnings)