WASHINGTON (CNN) -- The CEO of a company whose employee is accused of improperly looking at the passport files of presidential candidates is a consultant to the Barack Obama campaign, a source said Saturday. John O. Brennan, president and CEO of the Analysis Corp., advises the Illinois Democrat on foreign policy and intelligence issues, the source said. Brennan briefed the media on behalf of the campaign this month. The executive is a former senior CIA official and former interim director of the National Counterterrorism Center. He contributed $2,300 to the Obama campaign in January.