The Obama administration has confirmed the National Security Agency has used a secret “backdoor” allowing it to search for the emails and phone calls of U.S. citizens without a warrant. Citing documents leaked by Edward Snowden, The Guardian revealed last year an undisclosed rule change that allows NSA operatives to hunt for individual Americans’ communications using their names or other identifying information. In a new letter to Senator Ron Wyden obtained by The Guardian, the nation’s top intelligence official, James Clapper, confirms the “backdoor” loophole’s use. Clapper does not specify how many backdoor searches have been carried out. In a statement, Wyden called the warrantless searches “unacceptable” and “a real threat to the privacy rights of law-abiding Americans.”