Revealed: the top secret rules that allow NSA to use US data without a warrant - Guardian

Top secret documents submitted to the court that oversees surveillance by US intelligence agencies show the judges have signed off on broad orders which allow the NSA to make use of information "inadvertently" collected from domestic US communications without a warrant. - Revealed: the top secret rules that allow NSA to use US data without a warrant
Skype's secret Project Chess reportedly helped NSA access customers' data - The NSA files