A new analysis says the NSA collection of phone records actually does very little to prevent terror attacks.  

The New America Foundation, a non-profit group in Washington DC, says it has analyzed 225 terrorism cases in the US since the 9/11 attacks, and it found the bulk collection of phone metadata "has had no discernible impact on preventing acts of terrorism."

It says in the majority of cases, regular law enforcement and investigations found the evidence to bring cases against suspected terrorists.

A White House-appointed review board has come to a similar conclusion.

--Rob Archer