13 years post-9/11, has terror threat changed?

Thirteen years after the Sept. 11 terrorist attacks, Secretary of Homeland Security Jeh Johnson tells CBS News it's still a "dangerous world."

"The terrorist threat is more decentralized, it's more diffuse, so in many respects the terrorist that we face today is more complex," Johnson said in an interview with CBS News correspondent Michelle Miller.

Threats do not come from Islamic State of Iraq and Syria (ISIS) alone, but those on U.S. soil seeking to lend any terrorist a hand, he said.

"The issue of Syrian foreign fighters is always topic-number one in our discussions, and so we're tracking these individuals," Johnson said. "Several have been arrested by the FBI who've attempted to leave this country to take up the fight in Syria."

Johnson said domestic, homegrown terrorists are in many respects harder to detect than threats from overseas.

"The independent actor, who is inspired by violence because of something they read or something they see at home in their own living room, can strike without a whole lot of notice," Johnson said. "And so one of my priorities as secretary is community outreach, and it's worked with considerable success in some context but we need to do a better job."