He says finding that out will be crucial. "Whether this was an act of terrorism conducted by al-Qaida central or that of a lone wolf acting independently, we will have to wait and see for the investigation and what comes out of that, but we do know that al-Qaida and their affiliates have a crazed obsession in targeting the aviation industry,"

VOA: standard.2009.12.27

Levin said one challenge in protecting Obama is that the identity of a potential attacker would likely be unknown -- a person who believes in white supremacist ideology, but decides to act as a lone wolf.

CNN: White supremacists watched in lead up to Obama administration

Two sections of the Patriot Act the "lone wolf" provision and "roving wiretaps" (both requiring authorization by a special court) were created precisely to identify and monitor an individual like Tamerlan Tsarnaev before he detonates a bomb in a crowded public place.

WSJ: Henninger: Boston and the Un-Bush