Homeland Security Secretary Janet Napolitano issued her strongest public comments yet on the homegrown threat."We've seen an increased number of arrests here in the U.S. of individuals suspected of plotting terrorist attacks, or supporting terror groups abroad such as Al Qaeda," Napolitano said in a speech in New York. "Home-based terrorism is here. And, like violent extremism abroad, it will be part of the threat picture that we must now confront."Officials acknowledged that her tone had changed, though they said terrorism has been her focus since becoming Homeland Security chief.