Today marks eight years since the horrific attacks of 9/11. Most law enforcement officials will tell you the country's security has improved after the attacks. Al Qaeda has been degraded and many of its leaders have been killed.
But on matters of terrorism, there is always a caveat. U.S. pressure has forced al Qaeda into a more decentralized organization in which its major leaders, such as Osama bin Laden and Ayman Zawahiri, probably are not directing specific attacks.
Still, the group retains enough people and infrastructure to remain "lethal," officials said. And U.S. intelligence officials also worry about groups and individuals around the world who are inspired by al Qaeda, even if they don't report directly to its leadership.
There are indications this worry may be very well-founded.
In a July interview with ABC News, Attorney General Eric Holder said he was troubled by the emerging threat.
"The whole notion of radicalization is something that didn't loom as large a few months ago ... as it does now," Holder said. "And that's the shifting nature of threats that ... keeps you up at night."
Officials Claim Disrupted Plots by Radicalized Americans
What was Holder talking about? Here are some specifics:
This summer, a 26-year-old Long Island, N.Y., man was charged with attacking U.S. soldiers in Afghanistan and providing al Qaeda with details about the New York transit system. Investigators suspect he was radicalized in the United States and overseas.
Then, in sleepy Caswell County, N.C., seven men, most of them in their 20s, were accused of training to become terrorists. The FBI said the men were recruited to fight overseas by 39-year-old Daniel Patrick Boyd, who fought in Afghanistan against the Soviets in the late 80s.
In June, an Arkansas man and recent Muslim convert was charged with killing a U.S. Army recruiter in Little Rock, Ark., a day after viewing radical Islamic videos. The suspect is believed to have traveled in Yemen.
The FBI is conducting a massive investigation to find out who convinced 20 young Minneapolis men of Somali descent to fight in a civil war in Somalia.
FBI officials said it proves that there still are radicalized recruits out there who might be convinced to attack the United States at home. If such people cannot be found and neutralized before they attack, there are a host of "soft targets" in a democratic, free society that remain vulnerable, such as hotels or malls.
Where Things Stand: The Experts Weigh In
Here are some reflections about where things stand from homeland security, law enforcement, intelligence officials and other experts. Issues of chemical and port security and interoperability of different security systems top the list of concerns and gaps that some experts cite.
"The kind of vulnerabilities that were revealed to us on 9/11 clearly persist," said Stephen Flynn, senior fellow for counterterrorism and national security studies at the Council on Foreign Relations. "We still have a heavy concentration of chemical facilities near large population centers working with potentially very deadly substances. ... The risk of exposure of people potentially downwind is enormous."
In a July 29, 2009, speech in New York, Department of Homeland Security Secretary Janet Napolitano said, "While the terror threat is ever-changing, it is critical to reiterate that the threat remains. The consensus view of the intelligence community, of which DHS is a member, is that the terror threat to the homeland is, quote, 'persistent and evolving.'
"The threat of a nuclear or radiological device is of grave concern, and reducing that threat is a key administration priority. But we must be equally prepared for biological or chemical threats, which are capacities al Qaeda has sought for years." Napolitano said.
While the United States has made substantial efforts to harden borders by preventing potential terrorists and individuals on watch lists from gaining entry into the United States, the issue of illegal migration and border crossings continues to be a substantial threat.
In her July speech before the Council on Foreign Relations, Napolitano said, "We are also keenly aware that illegal immigration is not only a matter of sovereignty but could pose a national security threat, as well. The reality that potential terrorists could use a variety of ways to enter the country illegally -- fake documents, visa overstays and even border tunnels -- make this so."
In July, former members of the 9/11 commission, after meeting with Napolitano, estimated that about 80 percent of their recommendations issued five years ago had been fully enacted.
Contacted on Thursday, former 9/11 commissioner Fred Fielding, who was also White House counsel under President Bush in his second term, said, "We are safer ... but we are not there yet."
People and Packages: What's Coming? What's Going?
While DHS has established the US-Visit Program to gather biometric fingerprints and pictures of non-U.S. citizens entering the United States, the monitoring of who has been leaving the country is something that has not been handled effectively, according to some intelligence analysts.
Former 9/11 commission co-chairman Lee Hamilton said July 24, 2009, after meeting with Napolitano, "There has been quite a bit of progress ... that has been made with regard to entry. The exit problem, so far as I know, has not really been addressed at this point, and that will be a challenge for the department."
The United States has developed and maintained huge databases to assist and detect any nexus to terrorism ranging from the terror watchlist to shipping manifests.
In 2006, then-DHS Secretary Michael Chertoff oversaw efforts to have the United States receive significant amounts of airline passenger data (passenger name records) in efforts to screen for potential terrorists who may not be on various watchlists maintained by U.S. law enforcement and intelligence agencies.
Passenger data includes information in more than 30 fields, including reservation information, who booked the flight, payment methods and telephone information provided as part of the reservation booking. Passenger data is more thorough than flight manifests, which DHS officials use to check against terrorism watchlists.
The continuing vulnerabilities in port security is one area that counterterrorism experts and U.S. officials have expressed concern about. DHS has set up several key programs over the past few years, such as the Container Security Initiative and the Customs-Trade Partnership Against Terrorism plan, which increases information sharing with shippers.
"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.
What If There Were an Attack?
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."