WASHINGTON – Homeland Security and Governmental Affairs Committee Chairman Joe Lieberman, ID-Conn., and Ranking Member Susan Collins, R-Maine., Tuesday warned the American people not to lower their guard against terrorism now that the tenth anniversary of 9/11 has passed.

At the Committee’s annual hearing to assess the terrorist threat against the U.S., Homeland Security Secretary Janet Napolitano, FBI Director Robert Mueller and National Counterterrorism Center Director Matthew Olsen agreed that while al Qaeda’s leadership has been degraded, the terrorist threat was more “complex and diverse” than it was 10 years ago, and violent Islamist extremists working by themselves in this country, perhaps U.S. citizens, posed a particular threat.

“The ninth anniversary of 9/11 did not get the kind of attention we saw from the media last week. And neither will the 11th,” Lieberman said. “And even though we were reminded with fresh threat warnings over the past few days, there is evidence that America is already beginning to forget how real the threat of Islamist extremism really is.

“In some ways we may be the victims of our own success because there has not been another mass-casualty terrorist attack on American soil since 9/11 – something that, ten years ago, no one would have predicted.

“So the question we ask today is not ‘are we safer?’ – it is evidently clear we are safer – but ‘are we doing enough to stay safe?’”

Collins said: “We shall never forget those we lost on September 11th, 2001.  As has been noted often, the terrorists only have to get it right once; we have to be right every time or suffer the consequences of an attack. We are much safer than we were a decade ago, but we must be relentless in anticipating the changing tactics of terrorists.  As the successful decade-long search for Osama bin Laden proved, America’s resolve is the most powerful weapon against those who seek to destroy our way of life.”

All three witnesses testified that the specific, credible, but uncorroborated threat that was disclosed in the days leading up to 9/11/2011 continues to be investigated.

A Gallup poll taken before last year’s midterm elections showed terrorism ranked sixth in voters concerns – behind the economy, jobs, government corruption, federal spending and health care. Last week a study published by the Cato Institute called for abolishing the Department of Homeland Security.

“Some have taken the lack of another large-scale attack as evidence that the U.S. government exaggerated the danger posed by Islamist extremism and ‘overreacted’ in the wake of 9/11,” Lieberman noted. “I believe this is profoundly mistaken and ultimately irresponsible. We have weakened our enemies but they are not vanquished. That’s why our vigilance must be constant and not tied to the media attention for a particular anniversary.”

In 2011, alone, at least five homeland plots were broken up. Although the nation has suffered no major attacks like 9/11 in the past decade, two Islamist attacks killed Americans inside America both in 2009: the Fort Hood shooting and the shooting of an Army recruiter in Little Rock, Ark.

The Congressional Research Service has reported that, between May 2009, and July 2011, the last two years, 31 arrests were made in connection with “homegrown” plots by American citizens or legal permanent residents of the United States. Many had direct contact with al Qaeda or other violent Islamist groups in Yemen, Pakistan and elsewhere.

By comparison, in the more than seven years from September 11, 2001, through May 2009, there were only 21 such plots.