The National Security Agency (NSA) collected over 151 million phone records of Americans in 2016, despite a new system created by the US Congress to limit the spy agency's ability to gather bulk data, a report released by the Office of the Director of National Intelligence (DNI) revealed on 2 May.

The government report detailed that the NSA amassed vast amounts of data under a new system, despite having been court ordered to only use the system to apprehend 42 terrorism suspects in 2016.

The New York Times reported that Alex Joel, the chief civil liberties and privacy officer at the DNI, acknowledged that the number of targets seemed small "when compared to the very large number of call detail records generated by those targets".

"We believe the number of unique identifiers within those records is dramatically lower," he said.

The report also revealed that on one occasion in 2016, the FBI reviewed information about an American, whose data had been collected by the NSA under its surveillance programme. However, the report failed to mention how often the NSA shared information with the FBI and other intelligence agencies when conducting investigations.

The report comes just days after the NSA said it will stop its secret, warrantless collection of Americans' emails, which was hailed as a victory by privacy advocates who had long warned about the invasive nature of the agency's spy programme. The report also comes as the US Congress mulls over whether to renew Section 702 of the Foreign Intelligence Surveillance Act (Fisa), which is set to expire on 31 December 2017.

NSA and CIA searched for over 5,000 US persons in the 702 foreign intelligence database. pic.twitter.com/Sm5PJRCNAw Why advertise with us May 2, 2017

At the recent House Judiciary Committee hearing on Section 702, the committee's top Democrat Rep John Conyers took the intelligence community to task for failing to provide an estimate of the number of US citizens' communications collected by the NSA. "The intelligence community has not so much as responded to our December letter" asking for an update on the timing of the estimate, he said, according to a live blog of the hearing by EFF (Electronic Frontier Foundation). "I had hoped for better."

What is Section 702?

Section 702 of the Foreign Intelligence Surveillance Amendments Act is a law that allows US federal agencies to gather information without a warrant from phone and internet companies, on Americans. However, the target of the data collection must be a foreigner who happens to be communicating with someone within the US. The law also authorised programmes like the NSA's Prism and Upstream, which are widely considered to be some of the most intrusive surveillance programmes run by the spy agency.

In 2013, the NSA's spying powers were revealed by Edward Snowden and two years after the leaks, the US Congress created the US Freedom Act to curb the agency's bulk data collection.

Estimated number of targets under a single 702 order has crept up beyond 100,000: pic.twitter.com/ATrf2vFB60 — Jenna McLaughlin (@JennaMC_Laugh) May 2, 2017

Unmasking

The DNI report also detailed how often intelligence reports compiled by the NSA, come with revelations of Americans' identities, also called unmasking. Such reports are generally designed in a way to camouflage the identities of Americans, unless unmasking them is required to understand foreign intelligence.

According to the report, the NSA released over 3,900 reports in 2016, which included information on Americans gathered via its warrantless spy programme. Around 1,200 of those reports included unmasked identities of Americans. In response to requests, the NSA also unmasked more American identities in 1,934 additional reports.

The report also revealed that the number of foreigners abroad targeted by the NSA grew in 2016. While the number in 2015 was 94,000, it increased to 106,000 last year. However, certain forms of surveillance requests and techniques have reduced. For instance fewer NSL (National Security Letters) have been issued. The use of "pen register/trap-and-trace" orders used to collect metadata about the communications of specific targets has also gone down. The report said that intelligence court orders were obtained for 456 targets in 2015. In comparison, only 41 such orders were obtained in 2016.

Although the DNI report's revelations about NSA's spying on Americans highlights that the agency does still collect vast amounts of data, previous reports indicate that the numbers have gone down. According to a 2014 government report by the privacy and civil liberties oversight board, the NSA under its older system collected "billions of records per day with full knowledge that virtually all of them are irrelevant".

However, the DNI report's revelations may likely play a crucial role in the Congress' decision on whether Section 702 should be reauthorised at the end of the year.