ISIS in U.S. Prefer Twitter Among Social Media

Islamic State is renowned for its ability to mobilize followers via social media like Twitter, but the group is also attracting clusters of American followers who meet in person and push one another toward violence, experts and law-enforcement officials say.

A study published Tuesday by George Washington University’s Program on Extremism examined cases involving Americans charged with terrorism for their suspected support of Islamic State and found their conversion to the group’s world view often involved a significant amount of direct contact with “pre-existing social contacts who already embraced jihadist ideology.”

Concerns over threats from small groups of terrorist sympathizers have taken on a new urgency following last month’s attacks in Paris, which were carried out by people whose friendships and family connections appear to have formed the backbone of one or more terrorist cells.

Since the attacks, which killed over 100 people, the Federal Bureau of Investigation has upped its surveillance of known Islamic State supporters. U.S. counterterrorism officials say they haven’t uncovered any terror network or trained operatives in the U.S. like those who operated in Paris. Nor have they seen an uptick in the threat from people who might be inspired by the Paris bloodshed to launch copycat attacks, though they caution it is too early to measure that accurately.

About 70 people have been arrested in the U.S. on charges tied to Islamic State since early 2014, with investigations continuing in all 50 states, according to law-enforcement officials. Fifty-six people were arrested in 2015 alone, the largest number of terror arrests in a year since the Sept. 11, 2001 attacks, the report said.

Tracking such suspects is a labor-intensive effort that has stretched thin the agencies charged with preventing attacks. The case load was so heavy in the spring and summer that the FBI had to pull agents off of criminal work to assist in terror cases. Director James Comey has called that unsustainable over the long term.

But since July, the pace of new prosecutions has slowed, and the number of Americans trying to travel to Syria has dropped from about two a week to about two a month, according to officials.

Nineteen people have pleaded guilty, including seven who have already been sentenced to prison time, according to the Center on National Security at Fordham University’s School of Law, which also tracks ISIS cases. The rest are working their way through the courts.

The researchers at George Washington University said they have identified approximately 300 American supporters of the terrorist group, also known as ISIS or ISIL, on Twitter, the social-media platform of choice for many of the group’s supporters. The report also identifies two unnamed clusters of Islamic State-supporting friends, and the investigations are ongoing.

“ISIS is really good at motivating that single person to go out and do something, but…not many people act out in a way that’s truly alone. What we see more often are small cells,” said J.M. Berger, a counterterrorism expert and a nonresident fellow at the Brookings Institution, a think tank.

One cluster of friends in Texas “revolves around a few charismatic individuals and an Islamic studies group,’’ the report said. “Another, based in the suburbs of a large Midwestern city, appears to be composed of former high-school friends and a handful of their acquaintances.’’ The researchers didn’t further identify the groups as they said they didn’t want to interfere with potential criminal investigations.

Some clusters of alleged Islamic State supporters in the U.S. have been exposed by investigations. Federal prosecutors this summer brought a series of cases against five friends living in New York and New Jersey who allegedly pledged allegiance to Islamic State and were plotting to travel overseas to fight for the group.

Communications on social media began as early as 2012 between defendants Nader Saadeh, of Rutherford, N.J., and Munther Omar Saleh, of Queens, N.Y. As their discussions developed into the following year, they talked about their desire to build a “small army” of friends to fight against America, according to the indictments.

The group incorporated more people and began meeting together to watch Islamic State beheading videos and discuss plans to go overseas, prosecutors said. Some defendants were meeting on almost a daily basis between May and June, during which Mr. Saadeh flew from John F. Kennedy Airport to Amman, Jordan, with the intention of joining Islamic State, the indictments alleged.

Two defendants in this case have pleaded guilty to conspiracy charges, and Nader Saadeh is in plea negotiations, court papers say. Cases against the remaining two defendants, including Mr. Saleh, who have pleaded not guilty, are pending. Deborah Colson, the lawyer for Mr. Saleh, said: “We ask that the public withhold judgment until all of the facts are revealed.” Lawyers for the other defendants didn’t respond to requests for comment.

Defendants linked to Islamic State have posed unprecedented law-enforcement challenges. They are, on average, 26 years old, but have been as young as 15, younger than terrorism suspects charged in the U.S. in the past, the report says. Most of them are male, but the report says women, who make up almost 15% of the arrests, “are taking an increasingly prominent role.” Converts to Islam are overrepresented, comprising 40% of those arrested. The majority of suspects charged are U.S. citizens or legal residents, “underscoring the homegrown nature of the threat,” the report said, which said some clusters are organized around ethnicity.

Social media, particularly Twitter, play a big role. Online “spotters’’ engage with people posting general questions about religion, says the report, which described an exchange that started as a calm discussion of faith before “hardened ISIS supporters slowly introduced increasingly ardent views into the conversation.’’

A spokesman for Twitter Inc. said in a statement, “Violent threats and the promotion of terrorism deserve no place on Twitter, and our rules make that clear,” and pointed to Twitter’s terms of service, which say the firm will “take action” on accounts that threaten or promote violence.