James Clapper, John Brennan, Robert Mueller, Philip Goldberg, Michael Flynn, Matthew Olsen

A Senate committee hears about the top worldwide terror threats of 2013.

FOX News Radio's Steve Taylor reports in our ongoing series on national security:

Securing America.

The Director of the National Counterterrorism Center says the centralized al-Qaeda that attacked on 9/11 is not the threat it once was, but...

(Olsen) "Affiliated groups and groups sympathetic to al-Qaeda and al-Qaeda's message have grown in areas, for example, in North Africa."

Matthew Olsen also says the greatest risk of terror attacks inside the U.S....

(Olsen) "Likely comes from home-grown extremists who may well be inspired or radicalized by the message that al-Qaeda sends."

Olsen appearing Tuesday before the Senate Intelligence Committee.

In Washington, Steve Taylor, FOX News Radio.