A new report shows that the NSA has built a surveillance network that covers more of Americans' Internet activity than previously disclosed.
The system has the capacity to reach nearly 75 percent of all U.S. Internet traffic in the hunt for foreign intelligence, including communications by foreigners and Americans alike.
In some cases, it retains information from those communications and also filters domestic phone calls made within the United States.
The filtering targets communication that either originates or ends abroad. Officials say the system's broad reach makes it more likely that domestic communications will be intercepted and collected.
The NSA has continued to defend its practices as legal. NSA spokeswoman Vanee Vines said if American communications were "incidentally collected" the agency follows approved "minimization procedures."
The NSA programs are overseen by the secret Foreign Intelligence Surveillance Court. NSA is required to destroy information on Americans that doesn't fall under exceptions to the rule, including information that is relevant to foreign intelligence, encrypted, or evidence of a crime.
That means most of the data is discarded -- but not all of it. Some communications between Americans are stored within the NSA database.
Some civil liberties advocates have said that given the volume of information the NSA is examining, it is inevitable that a lot of data on Americans is stored, and the protection for those people is insufficient.
In 2012, Sen. Ron Wyden sought but failed to prohibit the agency from searching its databases for information on Americans without a warrant.
He also pushed intelligence agencies to detail how many Americans' communications have been collected and to explain whether purely domestic communications are retained in NSA's databanks. They have declined.
"Technology is moving us swiftly into a world where the only barriers to this kind of dragnet surveillance are the protections enshrined into law," Wyden said.
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