U.S. counterterrorism officials are claiming major inroads in reducing the likelihood of a successful terrorist attack. But officials also say the nature of the terrorist threat has changed significantly since 2001.
Some analysts have said the United States has been lucky to escape serious major terrorist attacks since the 2001 airplane attacks on the World Trade Center and Pentagon.
Last December 25, Umar Farouk Abdulmutallab tried to set off a bomb hidden in his underwear while on a flight from Amsterdam to Detroit, Michigan, but the bomb did not go off. Similarly, a bomb hidden in a car in New York's Times Square June 21 also failed to detonate. And in October bombs were discovered in inkjet cartridges aboard two cargo planes before they could be detonated.
In a recent speech National Counterterrorism Center director Michael Leiter said aggressive counterterrorism measures have eroded, but not eliminated, the terrorist threat.
"Despite the challenges we face, we have made significant improvements," said Leiter. "And the result of that is, in my view, that the threat of that most severe, most complicated attack is significantly lower today than it was in 2001. I have to stress, that threat is not gone."
But he added that one has to admit that at some point, some terrorists will launch a successful attack.
"I have dedicated my time at NCTC, and our organization dedicates our time, to trying to prevent that," added Leiter. "But we still have to be honest, and we have to be honest that some things will get through. And in this era of this more complicated threat and a more diverse threat and lower-scale attacks, to include individuals who have been radicalized here in the homeland, stopping all of the attacks has become that much harder."