ASPEN, Colorado — ISIS' effort to inspire troubled Americans to violence has become more of a terror threat to the U.S. than an external attack by al Qaeda, the FBI director said Wednesday.
FBI Director James Comey told an audience at the Aspen Security Forum that ISIS, which has proclaimed a caliphate in parts of Syria and Iraq, has influenced a significant but unknown number of Americans through a year-long campaign on social media urging Muslims who can't travel to the Middle East to "kill where you are."
Twitter handles affiliated with the group have more than 21,000 English-language followers worldwide, he said, thousands of whom may be U.S. residents.
The FBI has arrested a significant number of people over the last eight weeks who had been radicalized, Comey said, without specifying a number. He repeated his previous disclosure, without elaborating, that several people were arrested who were planning attacks related to the July Fourth holiday. The bureau has hundreds of investigations pending into such cases across the country.
Comey said it was too soon to say how Muhammad Youssef Abdulazeez, the Chattanooga gunman who killed five U.S. servicemen last week, became radicalized.
Abdulazeez's relatives have said he had a history of drug use and depression. Comey noted that "the people the Islamic State is trying to reach are people that al Qaeda would never use as an operative, because they are often unstable, troubled drug users."
Asked if the threat from ISIS had eclipsed that of the rival organization that attacked the U.S. on September 11, 2001, Comey said, "Yes."
The U.S. has tracked dozens of Americans, ranging in age from 18 to 62, who have traveled to Syria or Iraq to fight with the Islamic State group, he said.
"I worry very much about what I can't see," Comey added, because he said ISIS recruiters use encrypted communication software to avoid U.S. eavesdropping.