(REUTERS) - Top US security officials say the Internet has become a gem for terrorist organizations.

Speaking at a House committee hearing on Capitol Hill, Department of Homeland Security Secretary Jeh Johnson and FBI Director James Comey said terrorists are successfully using social media to further their cause.

"Today with new and skilled use of the Internet, terrorist organizations may publicly recruit and inspire individuals to conduct attacks within their own homelands," said Johnson.

Comey says the increase in the use of social media by terrorist organizations has taxed U.S. resources.

"In the spring of this year, when suddenly we had dozens and dozens of cases in the United States of people who are progressing along the spectrum from consuming to acting to killing where they are," said Comey.