"The Federal Intelligence Agency has succeeded in exposing a suspect Islamist among their employees", Xinhua news agency cited a local media report.
The man has made a partial confession. His goal was to infiltrate the Federal Intelligence Agency and gather information for a bomb attack on the main building in the German city of Cologne.
He had tried to pass on "sensitive information about the Federal Intelligence Agency, which could lead to a threat to the office".
He was "inconspicuous" during the application process, training and in his working fields, according to the authority.