In this Jan. 26, 2015 file photo, Secret Service officers search the south grounds of the White House in Washington after an unmanned aerial drone was found on the White House grounds during the middle of the night. Mysterious, middle-of-the-night drone flights by the U.S. Secret Service during the next several weeks over parts of Washington are part of secret government testing intended to find ways to interfere with rogue drones or knock them out of the sky.