Federal authorities are still on alert after news of a “specific, credible” terrorist threat for New York City and the District of Columbia broke on Thursday night, as the tenth anniversary of September 11 approached. The memorial service at Ground Zero still went on as promised Sunday, with thousands of people coming to the site to pay tribute to those who died and those who survived in the 9/11 attacks. Meanwhile, on Saturday the Taliban took credit for a suicide bomb attack on NATO forces in eastern Afghanistan, injuring at least 80 people. Larry Korb, senior fellow at the Center for American Progress, and former assistant secretary of defense under the Reagan administration, talks about whether Americans should still fear another terrorist attack.