As defined by the US FBI, 'the unlawful use of force against persons or property to intimidate or coerce a government, the civilian population or any segment thereof, in the furtherance of political or social objectives'
"The frequency and seriousness of international terrorist acts are often proportionate to the financing that terrorist groups might get." (1) Terrorist organizations must develop and maintain robust and low-key funding sources to survive.
The Foreign Intelligence Surveillance Act (FISA) allows the president to conduct instantaneous searches of suspected terrorists without a court warrant, so long as a court warrant is obtained within 72 hours after beginning the surveillance.
We have enough evidence now to tell us that this does not stop terrorism, may indeed provoke more terrorism, and at the same time leads to the deaths of hundreds, even thousands, of innocent people who happen to live in the vicinity of suspected terrorists.