"It's made some progress, but it's fundamentally an honor system," Flynn said. "It assumes that the commercial information that goes with a cargo container accurately captures where the container came from and what the contents are."
In January, DHS will be implementing additional security programs for maritime carriers called the Importer Security Filing, which will require 10 additional data collection points from importers and two data points from the shipping carriers.
Besides preventing attacks, there remains the question of how effective the response would be.
What resulted in the deaths of so many firefighters and police officers on 9/11 was the inability of first responders to communicate effectively with one another in the mass casualty. While some cities and municipalities such as New York and the Washington, D.C., area have been able to link systems with trunked radio and communication networks, many first responders around the United States still face problems of interoperability because of frequency and radio spectrum differences and lack of universal radio communication standards.
Last week at the National Press Club, Chertoff said, "We still have a ways to go. ... There are still variations in jurisdictions. ... Do you have governance plans that allow you to talk within your region?"
Chertoff said that with many different types of technology -- including VOIP, wireless and radio -- being used around the country, it eventually will be ideal for responders to have one uniform type of PDA.
"In the end, where we should be is to have ... responders have a BlackBerry or an iPhone or some comparable device ... to stream data, even video, so people can have situational awareness," Chertoff said.
While the development of watchlists, powerful databases and other sometimes controversial technology has assisted in preventing attacks in the United States, some officials say nothing can compete with good old-fashioned spy work.
"There is a view [that] there is a technological holy grail." Flynn said. "There is no substitute for gumshoe, intelligence, spook work."
In a message Thursday to CIA employees, CIA Director Leon Panetta wrote: "The CIA has inflicted major losses on a dangerous enemy. Places that al Qaeda once counted as safe havens have become less safe. People on whom al Qaeda once relied -- planners, commanders, facilitators and trainers -- have been taken off the battlefield. The information the CIA gathers and the actions it takes, crucial as they are, will not by themselves defeat terrorists determined to strike again. Al Qaeda's own vicious ideology, founded on the murder of innocent people, has proven to be a major weakness. But we cannot wait for popular disgust to isolate and overcome the extremists. We and our allies must continue to press the offensive, eroding their ability to plot and kill."