“The foreign signals that NSA collects are invaluable to national security,” the agency said in a statement released Friday to The Post.According to current and former counterterrorism officials and experts, NSA has become the single most important intelligence agency in finding al Qaeda and other enemy overseas after Septermber 2011 attacks in Washington.“This information helps the agency determine where adversaries are located, what they’re planning, when they’re planning to carry it out, with whom they’re working, and the kinds of weapons they’re using.”The Agency would initially track down drone targets by eavesdropping on telephonic conversations but was later asked to also track locations using phone signals.By September 2004, it could find cellphones even when they were turned off, reported Washington Post.Recent revelations about the mass of data collected, including phone and e-mail records by the spying technology resulted in an uproar at home and abroad.“These disclosures threaten to cause long-lasting and irreversible harm to our ability to identify and respond to the many threats facing our nation," said Robert S. Litt, general counsel for the Office of the Director of National Intelligence.The technology that was first made use of in 2001 to find drone targets had resulted in 200 civilian deaths by 2009 in Pakistan, Washington Post reported.