Electronic attack, also called electronic countermeasures, is part of electronic warfare, which uses of electromagnetic energy, directed energy, or antiradiation weapons to attack personnel, facilities, or equipment with the intent of degrading, neutralizing, or destroying enemy combat capability.
Electronic attack may attempt to "burn out" and permanently destroy its targets, but it is most likely to make it temporarily ineffective, with its users aware of that fact, or to make the target provide false information. The former is called, among other things, generic jamming, while the latter may be called deceptive jamming.
Meaconing is a specific form of deceptive jamming directed at navigational systems. It will receiving radio beacon, or navigational radar, signals and rebroadcasting them, on the same frequency to confuse navigation. The meaconing stations cause inaccurate bearings to be obtained by aircraft or ground stations. Meaconing also includes deception directed at active navigational aids, which, in normal operation, transmit a response signal on a different frequency than used to trigger the aid. In such cases, meaconing sends out a stronger faked response to confuse other receivers.
Targeting electronic attack
It will be necessary to know the opponent's electronic order of battle, including the types, locations, and operating characteristics of his electronics. At the tactical level, collecting such information is often called electronic support.
Electronic support may combine with signals intelligence (SIGINT) provided by higher-level organizations. SIGINT further divides into communications intelligence about radios and other human-oriented systems, and electronic intelligence against radar, electronic navigation aids, and weapons guidance systems.
High-power jammers also act as beacons identifying the position of the jammer. Air-to-air missiles, for example, often have a home-on-jam mode that overrides their tracking radar and sends them directly at the jammer. Ground jammers can easily be targeted by enemy artillery.
The ability to turn brute-force jamming against itself is a strong inducement to use more subtle deceptive jamming, disposable jammers or jammers on unmanned platforms, or multiple jammers among which signal transmission is switched.
Electronic attack can be directed against cellular telephony. In many countries, it is illegal for private individuals to interfere with such communications; the legal means of preventing cell phone use are restrictive to passive shielding against the radio signals used by the telephones. Some localities permit active jamming if its scope stays totally within the premises of the jamming operator.
Since cellular telephones have been used frequently to trigger improvised explosive devices, security and military organizations do use jammers, such as the AN/ALQ-30. That system is also capable of intercepting cellular telephony, and there is often a tradeoff between the value of communications intelligence gained from cellular traffic and the ability to interfere with an opponent's command and control.
One of the challenges, other than in governmental and military security such as that described above, is that commercial jammers are not specific to individual telephones. While there unquestionably is much annoying misuse of phones, and potentially privacy abuses by camera phones -- those without local storage unaffected by jamming -- the concern must be addressed that cellular communication is a legal service. There is a considerable body of law, long preceding the cell phone, that prohibits interference with lawful communications (e.g., U.S. Communications Act of 1934).
While it may be overly exaggerated, the scenario has been proposed that nonspecific jammer in a movie theater can also block legitimate emergency calls, both in and out. A patron with a medical emergency, who may not be able to summon assistance, will not be able to reach 911 or the appropriate national code for a universal emergency telephone number system.
Some jammer vendors ship only from a few countries, as more countries may prohibit the domestic sale or even manufacture of such devices.
Defending against electronic attack
A wide range of 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 (i.e., 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.