P. David Gaubatz, a former federal agent, is a U.S. State Department-trained Arabic linguist and counterterrorism specialist who has held the U.S. government's highest security clearances.Paul Sperry, a media fellow at Stanford University's Hoover Institution, is former Washington bureau chief forInvestor's Business Daily, and author ofInfiltration: How Muslim Spies and Subversives Have Penetrated Washington.