"It is fair to say there are individuals in the United States who ascribe to Al Qaeda-type beliefs," Napolitano told Bloomberg. "And so it makes information-sharing, it makes effective law enforcement and it makes the shared responsibility of law enforcement ever so important."
Napolitano said information among local, state and federal law enforcement agencies is "much improved" since the Sept. 11 terrorist attacks.
But, she warned that the threat of an attack is "always with us," Bloomberg reported.
Napolitano said a combination of killing or capturing some Al Qaeda leaders with the tracing or blocking of their finances has hampered the terror group geographically.
She said that has kept the main organization contained to northwestern Pakistan, but Al Qaeda is using affiliated groups to help plan attacks.