From New York Times:
WASHINGTON — For more than two years, a handful of Democrats on the Senate intelligence committee have warned that the government is secretly interpreting its surveillance powers under the Patriot Act in a way that would be alarming if the public — or even others in Congress — knew about it.
[…]
The dispute centers on what the government thinks it is allowed to do under Section 215 of the Patriot Act, under which agents may obtain a secret order from the Foreign Intelligence Surveillance Court allowing them to get access to any “tangible things” — like business records — that are deemed “relevant” to a terrorism or espionage investigation.