The US National Security Agency (NSA) will end the daily monitoring of millions of Americans' phone records by Sunday and replace the practice with more tightly targeted surveillance methods, officials have said. 

Mass surveillance under the microscope - The Listening Post

As required by law, the NSA will stop its wide-ranging surveillance programme just before midnight on Sunday. A new, scaled-back system is expected to be in place by the same time, the White House said on Friday.

The move comes two and a half years after the controversial programme was exposed by former NSA contractor Edward Snowden.

The change, mandated by a law passed six months ago, represents the greatest reduction of US spying capabilities since they expanded dramatically after the September 11, 2001 attacks.

Al Jazeera's Shihab Rattansi, reporting from Washington, said there was no evidence that the programme had thwarted any attacks on the US.

"It was completely useless and as the federal courts found out, it was completely unconstitutional ... because of Edward Snowden's leaks a debate began and light was shone on the programme," Rattansi said.

"There were people in the NSA themselves who said this was getting unwieldy."

Under the Freedom Act, the NSA and law enforcement agencies can no longer collect telephone calling records in bulk in an effort to identify suspicious activity.

Such records, known as "metadata," reveal which numbers Americans are calling and what time they place those calls, but not the content of the conversations.

Instead, analysts must now get a court order to ask telecommunications companies to enable monitoring of call records of specific people, or groups, for up to six months.

Source: Reuters And Al Jazeera