FBI counterterrorism investigators followed "dozens and dozens" of potential militants around the United States full time during the summer and "disrupted" many of them, FBI Director James Comey told a congressional committee on Thursday.
Comey, who testified before the Senate Committee on Homeland Security and Governmental Affairs along with Nick Rasmussen, director of the National Counterterrorism Center, said U.S. investigators are aware of dozens of U.S.-based Islamic militant suspects who now are using encrypted communications.
Comey said investigators had followed "dozens and dozens of people around the United States 24/7" during the summer and had "disrupted" them.
Comey told the committee that Islamic State recruits from the United States are incrementally younger with more "girls -women under 18" - seeking to join the militant group.
Rasmussen testified that Islamic State has overtaken al Qaeda as leader of the global violent extremist movement and has access to a large pool of potential recruits in Western countries.
He said counterterrorism experts still regard al Qaeda's Yemen-based affiliate AQAP as big threat due to its interest in attacking the United States and airplanes.