"There is probably some worry on the part of intelligence officials that bad guys have the ability to hit us are likely to hit us on a day like 9/11 to rattle our cages once again," former NYPD intelligence analyst Samuel Rascoff said.
It's also a time to assess how much New York's security has improved. The NYPD's counterterrorism force, with its undercover agents, special response units and analysts, rivals the FBI. Subway tunnels and stations have been significantly hardened and more bomb-sniffing dogs deployed. But according to a recent audit by the state comptroller, a critical "electronic subway security program remains far behind schedule."
"All we have to realize is that the favored target of terrorist is mass transportation look at London, Moscow and Madrid," transportation security expert Nicholas Casale said. "Over 250 attacks in the last five years against transportation."
Some 4,000 cameras have been installed throughout the subway and while they are fully operational, parts of the access and control system are not. Additionally, vital underground communication rooms frequently overheat. The entire half-billion dollar system is not expected to be fully operational until 2014.
"Well, I hope somebody tells Al-Qaida that so they don't attack until 2014. I mean, this is egregious," Casale said.
The good news 11 years later is that a 9/11 style attack on the city is less likely than just a few years ago.
There are no particular threats from any major terrorist organization, but the NYPD is taking security very seriously, particularly after new warnings about a possible lone wolf assault.
ABC News has obtained a law enforcement bulletin packed with the familiar warnings. But this year, there is no high alert. That's because there is less al-Qaida chatter, unlike last year, because the organization has less of a command structure holding it together.
"Twenty-three of the top 30 al-Qaida commanders are off the field, either dead or captured, in the two to three to four years," said Michael Breen, of the Truman National Security Project. "So this has been a pretty tough series of months and years for al-Qaida."
"The Al Qaida organization that hit us on 9/11 more or less is on the run to the point where it might not even exist years from now," Rascoff said.
Authorities aren't underestimating the lone wolf threat. The Times Square bomber is just one example. Police Commissioner Ray Kelly says the NYPD will be ready.
"We'll have our standard counter-terrorism overlay," he said. "You know, we have a special unit assigned to security of the memorial, so we feel that we're doing everything appropriate to secure it."
And the show of force on this anniversary isn't just homeland security theater. It's common sense.
"It is on everyone's mind and it's probably a good measure to beef up security to make sure the people have a sense that NYPD and FBI are all over the threat," Rascoff said.
Eyewitness News reporter Anthony Johnson and ABC News contributed to this report.
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