Revealed: the top secret rules that allow NSA to use US data without a warrant

Top secret documents submitted to the court that oversees surveillance by US intelligence agencies show the judges have signed off on broad orders which allow the NSA to make use of information "inadvertently" collected from domestic US communications without a warrant.

The documents detail the procedures the NSA is required to follow to target "non-US persons" under its foreign intelligence powers and what the agency does to minimize data collected on US citizens and residents in the course of that surveillance. The documents show that even under authorities governing the collection of foreign intelligence from foreign targets, US communications can still be collected, retained and used. The documents detail the circumstances in which data collected on US persons under the foreign intelligence authority must be destroyed, extensive steps analysts must take to try to check targets are outside the US, and reveals how US call records are used to help remove US citizens and residents from data collection.

However, alongside those provisions, the FISA court-approved policies allow the NSA to:

• Keep data that could potentially contain details of US persons for up to five years;
• Retain and make use of "inadvertently acquired" domestic communications if they contain usable intelligence, information on criminal activity, threat of harm to people or property, are encrypted, or are believed to contain any information relevant to cybersecurity;
• Preserve "foreign intelligence information" contained within attorney-client communications;
• Access the content of communications gathered from "U.S. based machine[s]" or phone numbers in order to establish if targets are located in the US, for the purposes of ceasing further surveillance.