U.S. intelligence analysts can use a secret National Security Agency program to scour wide-spanning databases tracking online traffic, the Guardian newspaper reported on Wednesday, citing documents from former NSA contractor Edward Snowden.
In training materials cited by the Guardian the NSA calls the XKeyscore program its "widest-reaching" system that covers "nearly everything a typical user does on the Internet."
Conducting surveillance through the program, according to the Guardian, requires "filling in a simple on-screen form giving only a broad justification for the search" and no review by a court or NSA staff.
A top secret NSA slideshow from 2008, posted by the Guardian on its website, showed that the program allowed analysts to access databases that collect and index online activity around the world, including searching for email addresses, extracted files, phone numbers or chat activity.
The 2008 slides did not address how analysts would get permission to use the tool on American targets. U.S. law requires specific warrants for surveillance of U.S. citizens but no warrant is required for communication involving foreigners.
The slideshow said XKeyscore program spans "approximately 150 sites" and "over 700 servers" around the world and intelligence from it had helped capture "over 300 terrorists."
Snowden's ongoing release of secret surveillance information to U.S. and European media has sparked an uproar in the United States and abroad over revelations that U.S. intelligence agencies collected data on phone calls and other communications of Americans and foreign citizens as a tool to fight terrorism.
"The implication that NSA's collection is arbitrary and unconstrained is false," NSA said in a statement in response to the Guardian's new report, calling XKeyscore part of "NSA's lawful foreign signals intelligence collection system."
NSA said "only those personnel who require access for their assigned tasks" are allowed to use the agency's analytic tools after completing regular training. "There are multiple technical, manual and supervisory checks and balances within the system to prevent deliberate misuse from occurring," it said.
Intelligence officials say NSA's programs help thwart terrorist attacks and that further secret document leaks threaten U.S. national security. But lawmakers have called for greater oversight of the vast surveillance system, which expanded rapidly after the September 11 attacks on the United States in 2001.
Snowden's passport has been revoked and he has been charged under the U.S. Espionage Act. He is stuck in limbo at a Moscow airport while seeking asylum in Russia, which has refused to extradite him.