September 24, 2001 | Source: Popular Mechanics

In the blink of an eye, electromagnetic bombs could throw civilization back 200 years. And terrorists can build them for $400.
An airborne “e-bomb” based on a Flux Compression Generator could generate an electromagnetic pulse (EMP) that could knock out electric power, computers and telecommunications.

The device consists of an explosives-packed tube placed inside a slightly larger copper coil energized by a bank of capacitors, creating a magnetic field that would collapse from a short created by an explosion. The result is the release of a powerful EMP.

A simpler version can be built by terrorists at low cost.

The only defense is electromagnetic shielding, which may be limited in effectiveness.