In electronic warfare, electronic protection measures can be used to defend against electronic attack. They may be passive, such as shielding one's own equipment, using highly directional antennas, or other techniques. Active defenses are often called electronic counter-countermeasures, and include making one's signal hard to detect and thus attack
Electronic protection can involve both deceptive decoys and sacrificial decoys. Decoys can be completely expendable, such as chaff and flares, or can be towed, such as the AN/ALE-55 towed by aircraft or the AN/SLQ-25 NIXIE towed by ships.
Towed decoys need an intelligent controller, such as the AN/ALE-47, which can integrate with defensive avionics such as radar warning receivers as well as helping the pilot with situational awareness of the threat. 
Active measures make the signal difficult to detect, and changes its properties frequently so the attack must constantly change. Methods include low probability of intercept, rapidly changing frequencies (i.e., frequency agility) or transmitting/receiving locations (e.g., multistatic techniques, mixing the signal with noise (i.e., spread spectrum), and a wide range of other methods.
- NAVAIR Electronic Warfare Software Support Activity (EWSSA), System Support: ALE-47