This past fall, al-Qaida's arm in Yemen tried its hand at a new kind of attack: cargo bombs.
The details of that plot are familiar by now. There were two bombs hidden in computer printer toner cartridges. They were then placed into boxes with clothing and other souvenirs from Yemen and shipped to Chicago.
That's what has been made public about the incident.
What intelligence officials are saying privately is that al-Qaida's arm in Yemen, the group that took responsibility for the attack, may have decided on cargo bombs for a very practical reason: It wanted them to succeed.
After watching low-level operatives bungle attacks all year, the al-Qaida in the Arabian Peninsula leadership may have been looking for ways to avoid rookie mistakes by directly managing plots themselves.
In this case, officials say, al-Qaida in Yemen's master bomb maker built two bombs for the cargo plot and then AQAP just mailed them. The process required no middlemen, risking fewer mistakes.
"One of the ways you can be more successful is take the human possibility of failure out of that chain," says Rick Nelson, who directs the national security program at the Center for Strategic and International Studies. "And I think that that is what you are seeing here -- individuals the leadership had hoped would conduct spectacular-like attacks ended up failing miserably."
Philip Mudd, a former terrorism official with both the CIA and the FBI, says that terrorists are searching for ways to take humans out of the equation. "But I don't think that will mean they will stop trying to insert people into Western Europe or the United States," he says. "There is no reason to believe that terrorist groups can't do two things at once. And anyway, a failure from our perspective is not a failure from their perspective. After all, on Dec. 25 last year and with the cargo attempts, they got tremendous international publicity."
The attempted attack on Dec. 25, 2009, involved a young Nigerian who allegedly tried to detonate explosives hidden in his underwear on a Detroit-bound trans-Atlantic airliner.
And while al-Qaida's arm in Yemen managed to eliminate the human factor in the latest cargo bomb plot, it also failed. But in this case it was only because U.S. intelligence got a lucky tip.
Michael Chertoff is a principal in the Chertoff Group, a security consulting firm, and the former secretary of the Department of Homeland Security. He says even though the cargo plot was foiled, it was still instructive to AQAP.
"They learn by failing, frankly. Things that don't work, they improve," he says. "If you look, for example, to the airline liquid bomb plot in 2006, that reflected the fact that we had raised barriers to bringing on metal detonators."
In the 2006 plot, terrorists figured out a way to get explosives onboard a plane without metal. They had liquid explosives hidden in soft-drink bottles. The liquid bomb plot is the reason passengers aren't allowed to carry on large bottles of shampoo and other liquids.
Counterterrorism officials are fond of saying that terrorists only need to get lucky once and security officials have to be right every time. Mudd says terrorists understand that, too.
"I don't think we should interpret their efforts to learn as an effort to become perfect," he says. "They are just trying to get better even while they are losing people left and right in the hopes that 1 out of 10 gets through."
Intelligence officials say they expect to be fending off smaller attacks next year as al-Qaida keeps trying to find cracks in the system.