Report: Nearly Half of American Jihadists are Not Fighting for ISIS

Group affiliations of non-ISIS U.S. jihadists include al-Qaeda and its global branches in the Arabian Peninsula and Maghreb, the Afghan and Pakistani Taliban, and other Qaeda-allied groups such as Al-Shabaab, Mali's Ansar Dine, and the Islamic Jihad Union in Uzbekistan.

"It is apparent that the U.S. is home to a small but active number of individuals inspired by the global jihadist movement, regardless of group affiliation," the report continues. "But the scale of the recent mobilization of U.S. citizens and residents in the cause of the movement is unprecedented."

On Sept. 11, House Intelligence Committee Chairman Devin Nunes (R-Calif.) warned that al-Qaeda "continues to metastasize."

"And, and I'm concerned that we're not paying close enough attention to the growth of radial jihadism globally," he told CBS. "...Al-Qaeda's very, very good at seeding people and waiting. They're very patient... They're spreading, they’re spreading, you know, globally, very, very slowly."

"We just don't know where these guys are hiding. And it's hard to track them because of encryption now on the internet. It's not as easy as what it once was a decade ago."