Experts say men such as Abdulmutallab, who live seemingly normal lives, are hard to identify and target.
"This is the truly disturbing part," Clarke said. "They are normal one day and then after a few weeks of watching the Internet and watching al Qaeda videotapes on the Internet, they become radicalized. They reach out in the real world for al Qaeda connections. They get trained.
"It's very hard to see these self-initiating terrorists become terrorists, very hard for U.S. intelligence to pick them up," Clarke added.
The United States needs to move quickly on identifying to whom Abdulmutallab was connected, and address the flaws in the security system that caused this to happen, experts said.
"It's clearly a wake-up call, and it's just like any other crime or criminal behavior. People are always trying to figure out ways around the system and al Qaeda or terrorists or people who want to blow things up are no different," Former FBI agent Brad Garrett told ABC News. "But, the key is: You want to sort that out as quickly as you can because if he is connected to someone else, what other bad acts might be out there waiting to happen?"
Clarke said the Obama administration needs to work more closely with the government of Yemen, which some say has emerged as the new front in terrorism.
"I think we do two things. Long term we work with our Arab friends in the area to address their economic problems and their political instability problems," Clarke said. "Short term, we work with CIA and Defense Department assets and the government of Yemen to go in and find these al Qaeda cells.
"And the untold story here is that the Obama administration is ahead of the curve. The Obama administration has been in Yemen working top CIA officials, top White House officials for over nine months now, working there trying to find these al Qaeda cells and they've done a good job of finding them and attacking them," Clarke said.
The Christmas Day terror attempt has sparked fears of additional bombers in the sky, and an incident Sunday was an indication that even a small matter can unleash a huge government response.
On the same Detroit-bound route two days later, a passenger who spent too much time in the bathroom after getting sick caused a full-scale security alert. Every inch of the plane was searched but the real issue turned out to be food poisoning.
As travelers head back home after the holidays in what is expected to be one of the busiest travel days this year, passengers can expect to see additional security measures and long lines, possibly even causing delays.
ABC News' Kirit Radia and Jason Ryan contributed to this report.