Support for the Islamic State of Iraq and Syria (ISIS or ISIL) increased after U.S. airstrikes began in Iraq and the militant group may take more hostages to try to force concessions from Washington, the FBI director told Congress on Wednesday.
ISIS is "committed to instilling fear and attracting recruits" and to drawing public attention, as shown through its use of social media and in videos it released of the beheadings of American journalists James Foley and Steven Sotloff, said FBI Director James Comey.
"ISIL's widespread use of social media and growing online support intensified following the commencement of U.S. airstrikes in Iraq," Comey, using an acronym for the group, said in prepared testimony for a congressional hearing on threats to the U.S. homeland.
ISIS and other outfits "may continue to try to capture American hostages in an attempt to force the U.S. government and people into making concessions that would only strengthen ISIL and further its terrorist operations," Comey said.
ISIS draws an estimated $1 million per day from black market oil sales, smuggling, robberies, and ransom payments for hostages, according to Matt Olsen, director of the National Counterterrorism Center.
The United States and United Kingdom, unlike some European nations, do not pay ransom for the release of hostages.
The group's ability to attack the U.S. homeland relies in part on its widespread and sophisticated use of social media to radicalize Americans, the national security officials told the House of Representatives Homeland Security Committee.
The group used these tools as it drew recruits from more than 15,000 foreign fighters in Syria, who may return to their countries "battle-hardened, radicalized and determined to attack us," Olsen, the top U.S. counterterrorism official, said in prepared testimony.
Syria remains a prime training ground for independent or al-Qaeda-aligned groups. "The rate of travelers into Syria exceeds the rate of travelers who went into Afghanistan/Pakistan, Iraq, Yemen or Somalia at any point in the last 10 years," he said.
The security officials testified as the U.S. military prepared to expand American-led action against ISIS to Syria, striking the militant group's safe havens in that country to knock out infrastructure, logistics and command capabilities.
They outlined threats to the United States from militant groups around the world, including more diverse and diffuse al Qaeda offshoots, and said they continued to focus on airline security to counter a primary target of attack.
Olsen singled out Al-Qaeda in the Arabian Peninsula, which was behind three attempted airline bombings, including the 2009 underwear bomber in Detroit, as the al-Qaeda offshoot "most likely to attempt transnational attacks" against the United States.
Despite that group's ambitions, Olsen said, "homegrown violent extremists remain the most likely immediate threat to the homeland."
Online recruitment and terrorism networks have been used to foster the threat from the homegrown, or "lone wolf" attackers, that Homeland Security Secretary Jeh Johnson identified as the hardest threat to detect and the one he worries about most.
AQAP claimed the accused Boston Marathon bombers, who killed three people and injured 264 when they set off pressure cooker bombs in April 2013, were "inspired by Inspire," the group's English language magazine, Comey and Olsen said.
The testimony showed that online propaganda enforcing a violent extremist ideology and teaching various bombing techniques may outlast any one leader of a militant group.
"This boundless virtual environment, combined with terrorists' increasingly sophisticated use of social media, makes it increasingly difficult to protect our youth from propaganda," Olsen testified.