It is well known that microprocessor-based equipment is susceptible to upset or damage by electromagnetic signals.

The relatively low levels normally encountered by equipment unintentionally transmitting electromagnetic (EM) signals are enough to cause interference or upset and fuel the Electromagnetic Compatibility (EMC) industry.

Using more intense signals, IEMI exploits the vulnerabilities of microprocessor-based systems to deliberately cause interference or destruction of components without physical contact. These devices, variously called non-nuclear EMP devices, Radio Frequency Weapons (RFW), High Power Microwave (HPM), High Intensity Radio Frequency (HIRF), or E-bombs, use much higher power pulses. This is a growing concern to the US and other national governments and international standards organizations. The IEC has produced international standards to define the threat and outline protection.

IEMI devices can be categorized into 2 broad categories depending on the type of signals they produce: narrow band and wide band. The narrow band devices focus their energy into a tight frequency distribution, generally exploiting a known coupling path to maximize their impact. Devices in this category include military high power microwave (HPM) weapons and off-the-shelf radar sets. The broad band devices are simpler to build and employ a very wide frequency distribution to maximize the probability that some part of the signal will find an efficient coupling path. The sophistication of devices varies widely. Plans and parts for powerful but simple devices can be readily purchased on the Internet. Equipment that has other uses can be converted or used to cause upset, for instance radar sets and magnetrons from microwave ovens. The most effective devices come from specialized areas of research and are available to knowledgeable individuals.