With news that the bombs used in yesterday's attack on the Boston Marathon were encased in six-liter pressure cookers, we've got our first clue about the tech that played a role in this attack
Reports of pressure cookers being used as bombs go back to at least the 1990s when they were first used by Maoists in Nepal during the civil war there, and they are still used in the mountain nation with alarming frequency. (In fact, do a quick Google search and you'll see that pressure cooker bombs are found all the time in South Asia from Nepal to Malaysia.)
By the 2000s, such weapons were being found across the region at terrorist camps on the frontier of Afghanistan and Pakistan. This 2004 warning from the Department of Homeland Security says that "a technique commonly taught in Afghan terrorist training camps is the use/conversion of pressure cookers into IEDs.
By 2010, DHS was reporting that such bombs were frequently used in Afghanistan, Pakistan, India, and Nepal. (Note this report from 2010 displaying a pressure cooker bomb found by British special operators after a raid on a Taliban bomb factory in Afghanistan.)
"Typically, these bombs are made by placing TNT or other explosives in a pressure cooker and attaching a blasting cap at the top of the pressure cooker. The size of the blast depends on the size of the pressure cooker and the amount of explosive placed inside. Pressure cooker bombs are made with readily available materials and can be as simple or as complex as the builder decides," reads the 2004 announcement. (Notice that the announcement says nothing about using the pressure of the pressure cooker, it's merely described as a vessel for the explosives.) While the DHS warning doesn't say exactly why pressure cookers are preferred over normal pots, their lids lock into place, perhaps making it easier to hide explosives inside.
Remember, doctors in Boston have reported removing "pellets, shrapnel and nails" from the victims of the marathon attack, indicating that the bombs were filled with these tools in order to cause more damage by shredding flesh.
"These types of devices can be initiated using simple electronic components including, but not limited to, digital watches, garage door openers, cell phones or pagers. As a common cooking utensil, the pressure cooker is often overlooked when searching vehicles, residences or merchandise crossing the U.S. Borders," the 2004 DHS announcement points out.
Still, the 2010 announcement notes that pressure cookers are not as innocuous in the United States as in developing nations: "Because they are less common in the United States, the presence of a pressure cooker in an unusual location such as a building lobby or busy street corner should be treated as suspicious."
That document was released several months after a pressure cooker filled with firecrackers was found to be one of the components used in the failed Times Square bombing of May 2010. In 2011, U.S. Army Private Naser Jason Abdo was charged in plotting to set off a pressure cooker bomb on Fort Hood, Texas -- a weapon he supposedly learned to make from reading al Qaeda's online magazine, Inspire. It's important to point out that investigators have said there is no indication so far of a connection to al Qaeda in the case of the Boston attack.
John Reed reports on the frontiers of cyber war and the latest in military technology for Killer Apps.