American authorities this year have arrested nearly five dozen people in the United States for helping to support or plot with the Islamic State, according to a new study, the largest number of terrorism-related arrests in the country in a single year since September 2001.
The Islamic State recruits defy any single profile, the study found, although they are younger than previous terrorism suspects, draw heavily on converts to Islam, and reflect increasingly prominent roles for women in the terrorist organization.
A demographic snapshot of the 71 individuals arrested on charges related to the Islamic State since March 2014, including 56 this year, emerged from a comprehensive review of social media accounts and legal documents of nearly 400 American sympathizers of the Islamic State conducted by researchers at George Washington University.
The volume and diversity of those arrested underscore the growing challenge the F.B.I. and local law enforcement agencies face in trying to identify, monitor and, if necessary, apprehend suspects at a time when the Islamic State has sharply increased its appeal to Westerners through Twitter, Facebook and other social media.
“The individuals range from hardened militants to teenage girls, petty criminals and college students,” said Lorenzo Vidino, the director of the university’s program on extremism, which conducted the study. “The diversity is staggering.”
The report, titled “ISIS in America: From Retweets to Raqqa,” was made public on Tuesday.
Even before the recent attacks in Paris, at least three dozen people in the United States suspected of ties to the Islamic State were under heavy electronic or physical surveillance, according to American officials. Those under investigation typically have little terrorism expertise or support from a cell, making it even more difficult for the authorities to predict or detect who might carry out a strike.
“For law enforcement, it’s extremely difficult to determine who makes a big leap from keyboard jihadist to doing something,” said Dr. Vidino, who has studied Islamism for 15 years.
The people in the George Washington University study ranged from a 15-year-old boy to Tairod Pugh, a former Air Force officer who was 47 at the time of his arrest. The average age of the American supporter of the Islamic State was 26, the report found, reflecting a pattern unfolding in other Western countries as social media attracts younger recruits.
Read more: NY Times