But critics say the system, in fact, may not be working.
"This is, in my view, is probably one of the worst situations I've ever heard of. And to cast this as the system working is not really what the American public needs to hear," former FBI agent Jack Cloonan said in an interview with ABC News.
And Republicans accused the White House of complacency amid a steady stream of attacks, including the deadly shooting at Fort Hood.
"The threat to the United States, is real. I think this administration has downplayed it. They need to recognize it, identify it," said Rep. Pete Hoekstra, R-Mich., on "Fox News Sunday."
Gibbs rejected that the administration is not doing all that it can to fight terrorism.
"The president is very confident that this government is taking the steps that are necessary to take – to take our fight to those that seek to do us harm," he said.
Federal law enforcement sources tell ABC News that the incident is a sobering reminder that the war against terrorism is a deadly game of chess, with terrorists becoming more creative all the time.
ABC News' Tahman Bradley, Jason Ryan, Richard Esposito, Michael S. James, and Reynolds Holding contributed to this story.