The "e-bomb" is to the digital world what kryptonite was to Superman: rare, elusive, and deadly to what we thought invulnerable. The e-bomb, as developed by engineers in the United States, Britain, and Russia, doesn't kill people or destroy buildings. Rather, it uses an electromagnetic pulse (EMP), microwaves, or radio frequencies to destroy electronic circuits from a distance. In friendly hands, it offers the tantalizing prospect of winning wars without hurting people. In enemy hands, it threatens a nightmare scenario of instantly blacked out stock exchanges, hospitals, airports, and even whole cities.

Although reports of U.S. Air Force e-bomb tests have leaked out since 1993, the Pentagon, as of Sept. 11, 2001, takes the same maddening "neither confirm nor deny" stance it assumes when talking about nuclear weapons.

"Our guys would love to talk about it, but we can't," says Conrad Dciewulski(cq) of the Air Force Research Lab at Kirtland Air Force Base, N.M., where scientists are working on both the offensive and defensive aspects of e-bomb warfare.

The Soviet army reportedly tested e-bombs as early as the 1940s, and the British defense firm Matra Bae Dynamics last summer announced it had developed a battlefield e-bomb that uses radio frequencies to cook enemy electronics.

American generals have been worrying and dreaming about EMP weapons ever since Test Shot Starfish in 1962, when the United States burst a 1.4 megaton hydrogen bomb 400 kilometers above the Pacific Ocean and unexpectedly knocked out radio communications and satellite equipment across thousands of miles.

"A member of the Russian duma recently told me, ‘You know, if we really wanted to hurt you, we would set off an atomic weapon at high altitude above your country and produce an EMP that would destroy your entire electrical power grid, computers, and telecommunications infrastructure -- including satellites,' " says U.S. Rep. Roscoe Bartlett (R-Md.).

Using a hydrogen bomb to take out electronics, though, is like using a chain saw to cut your toenails, hence the search for a more delicate tool. E-bombs are particularly attractive to the military in the era of ubiquitous media coverage. As a pair of Air Force officers wrote in the journal Air Power, "the CNN factor" makes limiting collateral damage and keeping casualties to a minimum almost as important as vanquishing the enemy. The Air Force let some Iraqi MiGs go unbombed during the Persian Gulf War because Saddam Hussein had tucked them beside ancient monuments the Pentagon wasn't willing to damage. E-bombs could have fried their circuitry while leaving antiquity unscathed. They also, incidentally, offer the prospect of a battlefield where TV cameras don't work.

Unfortunately from a defensive point of view, an e-bomb is a lot easier to build than a nuclear bomb, and they don't have to be delivered by sophisticated missiles. David Schriner, a former civilian electrical engineer for the Navy, told Congress in 1998 that he'd assembled $500 worth of automobile ignition coils, batteries, fuel pumps, and other assorted hardware in his basement, and in one week, he'd built an e-bomb that could make a running car hiccup at 50 feet by overloading its electrical system. Congress was sufficiently frightened to give Schriner a million-dollar contract to see if he could build a truly effective e-bomb out of readily available materials.

"Until you have one that can take out a whole building," says Schriner, "you don't have a credible weapon."

He has since built a "building within a building" at his Ridgecrest, Calif., engineering firm, and, with a more powerful device built around a telephone poll transformer the size of desktop printer, successfully shot through walls to scramble a collection of intravenous pumps and other electronic medical equipment. One device Schriner is building could shut down the financial markets indefinitely, he says, if hidden in an ordinary-looking van and parked outside the New York Stock Exchange. Another, built around a backyard satellite dish, would be capable of shutting down all of an airliner's electrical systems just as it's coming in for a landing. Still another could spray circuit-killing radiation in all directions from a van rolling through a city. Passersby wouldn't even notice until they glanced at their digital watches, tried to make a cell phone call, or noticed that every car on the road was gliding to a dead stop. Each device, Schriner says, is being built of ordinary stuff you'd find in Home Depot, auto parts stores, and consumer electronics catalogues.

At the urging of Bartlett, Congress last summer ordered Secretary of Defense Donald Rumsfeld to appoint a commission to study the EMP threat. You'd think Sept. 11 would add new urgency to the enterprise, but a shortage of Pentagon office space since attack has kept the commission from meeting.

Still, before you get too panicked at the thought of impending e-bomb warfare, keep in mind that defense against e-bombs can be as low-tech as the bombs themselves.

"It's pretty easy to shield equipment," says David Schriner. "Sometimes the fix is a 10-cent device like putting a ferrite doughnut around the mouse cord, but until people know about the threat, they can't do anything about it."