Section 215 allows the FBI to order any person or entity to turn over "any tangible things," so long as the FBI "specif[ies]" that the order is "for an authorized investigation . . . to protect against international terrorism or clandestine intelligence activities."
Section 215 vastly expands the FBI's power to spy on ordinary people living in the United States, including United States citizens and permanent residents.
The FBI need not show probable cause,
nor even reasonable grounds to believe, that the person whose records it seeks is engaged in criminal activity.
The FBI need not have any suspicion that the subject of the investigation is a foreign power or agent of a foreign power.
The FBI can investigate United States persons based in part on their exercise of First Amendment rights, and it can investigate non-United States persons based solely on their exercise of First Amendment rights.
For example, the FBI could spy on a person because they don't like the books she reads, or because they don't like the web sites she visits. They could spy on her because she wrote a letter to the editor that criticized government policy.
Those served with Section 215 orders are prohibited from disclosing the fact to anyone else. Those who are the subjects of the surveillance are never notified that their privacy has been compromised.
If the government had been keeping track of what books a person had been reading, or what web sites she had been visiting, the person would never know.
American Civil Liberties Union, 1/21/09,
http://action.aclu.org/reformthepatriotact/215.html