US intelligence chiefs have confirmed that the National Security Agency has used a “back door” in surveillance law to perform warrantless searches on Americans’ communications.The NSA’s collection programs are ostensibly targeted at foreigners, but in August the Guardian revealed a secret rule change allowing NSA analysts to search for Americans’ details within the databases.
http://www.theguardian.com/world/2014/apr/01/nsa-surveillance-loophole-americans-data