After attacks with airliners and assaults with anthrax-laced mail, security experts are pondering when — and how — future attacks may come.
Nuclear bombs, biological warfare and other "weapons of mass destruction" are scary possibilities, but some experts offer a lesser-known potential threat: E-bombs.
The good news about these so-called electronic bombs is they aren't directly harmful to humans or structures like buildings or bridges.
But the bad news for technological nations like the United States is that as the name implies, e-bombs go after electronic devices — computers, radios, telephones, and almost anything that uses transistors, circuits, and wiring.
Invisible and Instant Device-Killers
Powerful e-bombs can "kill" electrical equipment by rapidly creating and transmitting a huge burst of electrical energy into the atmosphere. That sudden explosion of energy results in an electromagnetic pulse, or EMP.
The circuits and wiring in electrical devices act like antennas and pick up the invisible EMP wave as it moves through the air. And depending on the distance from the explosion and the strength of the EMP burst, the affected electronics will either become temporarily disabled or completely overloaded and destroyed by the excess energy.
The destructive nature of an EMP was discovered during early American nuclear weapons testing. When an atomic bomb was exploded high above Earth in 1958, the sudden release of gamma radiation in the air resulted in a massive EMP wave. Street lamps as far away in Hawaii were blown out while navigation systems were disrupted for 18 hours by residual fluctuating interference.
Since then, scientists have researched EMP and other "directed energy weapons" and developed designs that don't require a massive nuclear explosion to create devastating EMP bursts. One such "conventional" EMP weapon, for example, is the so-called flux compression generator, or FCG.
It's a bomb that uses a tube of conventional explosives surrounded by a coil of copper wire. A battery charges the coil and creates an electromagnet. But when the bomb explodes, the electrically charged coil shorts out and compresses the magnetic waves into the destructive EMP.
The FCG doesn't create an EMP burst as strong or widely dispersed as a nuclear bomb exploded 30 miles above Earth. But an FCG could be built from commonly available electronic parts and reportedly for less than $1,000.
Not in the Terrorists’ Arsenal?
The potential for such weapons to cripple the United States hasn't been lost on government officials. Less than a month after the attacks on the World Trade Center and the Pentagon, President Bush announced the appointment of Richard Clarke to a new position of Cyberspace Security Adviser.
Clarke, along with members of the newly created Critical Infrastructure Protection Board, will seek ways to protect vital yet vulnerable information systems such as commercial communications networks.
Still, some defense and security experts doubt that EMP bombs would be the weapon of choice for terrorists.
For one, devices can be protected or hardened against EMP. Sensitive electronic circuits, for example, can be encased in Faraday cages — metal structures that intercept and redirect excessive EMP energy into the ground like a lightning rod.
Another mitigating factor in the minds of some experts is the limited effectiveness of conventional EMP weapons. Robert Sherman, a defense analyst with the Federation of American Scientists, says that small e-bombs like FCGs have to be placed very close to potential civilian targets such as a telephone center.
"If you can get that close to a communication node, you can just use a truck bomb," says Sherman. "There are a lot of other things that people should be worried about."