hen a car bomb exploded in the parking garage beneath the World Trade Center in 1993, it blasted away two reinforced levels, and left a 150-square-foot crater and a half-story pile of rubble.

Symbols like the Statue of Liberty and the U.S. flag have always symbolized freedom and security. All that changed after the World Trade Center bombing in 1993.

Cars that had been parked on the second level of the three-story crater were strewn like toys, their parts half-buried among the busted cinder blocks and crushed ventilation shafts that lay singed from an acrid electrical fire. The walls around the blast site were scorched.

Five people and one unborn child were killed.

But walls and lives were not the only things to disintegrate that gray Friday in February, eight years ago. The infamous blast blew away feelings of security once taken for granted in urban metropolises across the United States.

The explosion was ranked as the most violent terrorist attack in the nation's history, police and other law enforcement experts says.

In 1993, most multitenant commercial buildings were easy to access. People could enter lobbies and ascend elevators without showing I.D. and without set appointments. Garages under buildings were open to the public, and access was pretty much unlimited.

"We now know that a terrorist act is not only possible
– it has happened," says Jim Margolin, special agent at the Federal Bureau of Investigation's field office in Manhattan, whose own office has changed since the bombing. Strangers used to be able to take the elevator directly to the FBI cafeteria; that is not possible today.

"Generally there are more measures in place now for physical security of buildings and people than 10 years ago," Margolin says.

Bruce Hoffman, director of the Washington office of the RAND Institute, doubts the effect of the increased security. To receive a parking permit for the lot under the World Trade Center employees must submit to a background check. This includes a lifestyle check investigating personal debt - something that could make a person vulnerable to blackmailing, a practice Hoffman finds objectionable.

"One could conceivably question why they are doing background checks of their employees," says Hoffman, author of "Inside Terrorism." "It certainly doesn’t fit the modus operandi."

It might make people feel better, he says, but it doesn't improve security. "It’s rare that terrorists try to infiltrate organizations and get jobs."

"One improvement – if you can call it that," says Frank A. Bolz, a retired counterterrorism expert, is that people are now more aware that this kind of destruction can happen in the U.S.

"We are more aware – but more secure I don’t know," Bolz says, "For every step we take the terrorist groups take a step forward too. It is always a catch up."

Michael Rotardo is a deliveryman for Verizon. He says it is annoying to be photographed every time he makes his daily delivery to the World Trade Center.

Bolz, a former member of the New York Police Department explains that whereas some terrorist groups seems to have unlimited resources, those who are to fight them have to apply for funding and government resources.

Harvey Burstein, a former FBI agent who teaches courses on security at Northeastern University, agrees.

The most important thing, Burstein says, is for people to report anything suspicious, such as a package that has been left or a fire extinguisher that has been moved out of its usual place. It is important that people as well as systems notice things like a stranger wandering without purpose in a building.

"It’s like watching out for shoplifters." Burstein says. "Go up to the person and ask, 'may I help you,' if they are lost they should tell you what they are looking for – otherwise be suspicious and report what has happened, Burstein says.