Department of Homeland Security Secretary Jeh Johnson said the threat of “lone wolf” terror attacks has become his biggest fear, saying self-radicalized militants are much more difficult for law enforcement and intelligence agencies to detect.
Mr. Johnson, speaking at the Aspen Security Forum, said U.S. and foreign counterterrorism officials have had to adjust to the prevalence of “small scale attacks in increasing frequency,” both in the U.S. and Europe.
He specifically mentioned the December terror attack in San Bernardino, Calif., when a husband-and-wife team killed 14 people at a holiday party, and the mass shooting at an Orlando nightclub last month that killed nearly 50 people.