The director of the FBI says ISIS poses a bigger threat to the U.S. homeland than al Qaeda.

FOX News Radio's Rachel Sutherland reports from Washington:

They're not your parents' al Qaeda, that from James Comey, who says the use of social media sets ISIS apart.

(Comey) "The threat that ISIL presents, poses to the United States is very different in kind, in type, in degree than al Qaeda." 

The FBI boss told the Aspen Security Forum that ISIS is preaching through social media sites like Twitter, buzzing their messages on phones to "troubled souls"... Comey says Twitter handles associated with the group have more than 21,000 English-language followers worldwide.

In Washington, Rachel Sutherland, FOX News Radio.