Information Warfare

The idea of 'InfoWar' was first brought into the public eye at the 'Infowar Conference' a few years ago. One of the better reference sites on it is http://www.infowar.com.

This talk discussed some technical details on the weapons of infowarfare - in particular, EMP (Electro-Magnetic Pulse) bombs of all varieties. First, the standard disclaimers; all information in the talk came from public sources, and is for educational use only. Attempting to build or discharge an EMP weapon is likely to cause a large number of people in threatening suits and black sunglasses seriously to ruin your day.

There were four categories of InfoWar discussed:

flow manipulation : transmitting disinformation, releasing correct data at a time convenient for you and exceptionally inconvenient to your adversary, altering your enemy's data, deceiving his sensors, and editing the contents of his communication links in transit.
software attacks : the standard menagerie of viruses and Trojan Horses (the latter being particularly useful in a situation like the Gulf War, where your enemy has been your ally until relatively recently and has bought many of your systems), together with conventional hacking.
mechanical attacks : data isn't very good at travelling through substantial gaps in cables. There have been several attacks of this sort, probably because they're the easiest ones for a non-technical group to carry out; one set of people in Japan cut the wires communicating with the Bullet Train, and Keine Verbindung in Frankfurt cut a metre out of cables simultaneously at three points, wiping out links to the airport. There are various defences against these attacks; the German PTT responded to the Frankfurt incident by removing info about cables from normal access. Security through Obscurity works quite well for government agencies.
electromagnetic weaponry : this is much more interesting, and hence was discussed for the rest of the talk. There is a lot of apocryphal information around on the properties of electromagnetic attacks, and some very useful stuff around the Net; http://www.cdsar.af.mil/kopp/apjemp.html has an extremely detailed document, which sounds as if it's the source for much of this talk.

There are two types of electromagnetic effect which are interesting here: EMP and HERF (High Energy Radio Frequency). EMP was first detected at atomic-bomb tests, and induces power surges in conductors, destroying electronics connected to them. In fact, its effects are substantially greater than that; the USSR did a test in which a 200km power line 150km from Ground Zero had so much current induced in it by the EMP that it melted.

Around 1980, it became publicly known that non-nuclear EMP devices could be built, in particular a 'HERF gun' which was supposed to generate focused pulses; no-one has yet shown that this is possible.

The most straightforward EMP weapons consists of a magnetron (a device present in every microwave oven), attached to a vast capacitor bank to provide a current spike through it. Note that this is dangerous to anything water-containing in the neighbourhood, including people, so don't do it at home. No-one has publicly demonstrated a working one; however, there are various reports that a small portable version of this could be used by the police to stop cars by burning out their engine-control computers.

Nuclear EMPs produce a short, extremely high-energy pulse at relatively low frequencies; non-nuclear EMP weapons can't deliver anything like as much energy, but can deliver it at more interesting frequencies.

The study of non-nuclear EMP generation started in the 1970s, when it was described as 'high-energy physics'. They made their first public appearance inadvertently at Sandia Labs in the US, when an accidental discharge destroyed the electronics of the cars in the parking lot there.

EMP-generating warheads for cruise missiles and free-fall bombs exist; these would be very useful against radar stations and communications facilities, because they ensure that the expensive electronics is destroyed, rather than the cheap aerials or dishes used to transmit. They may well have been used for this purpose in the Gulf War; it would be interesting to see the warhead of an HARM missile.

Non-nuclear techniques

Nuclear bombs are hard to come by, so various other elaborate techniques are used to produce the necessary short high-powered pulses required to fire an EMP weapon :

MHD generator	You take a solid rocket motor, and add a little potassium to its fuel to ensure that the stream of high-speed gas coming out is ionised. You then arrange that the stream of gas passes through a coil, and use copper blocks in contact with the gas stream to extract power from it. In ideal circumstances, you can convert 60% of the kinetic energy of the stream of gas into electrical power. These generators have civilian applications; they allow you to build power stations with no moving parts, which is useful if you want to pump gas in Siberia. You can use a stream of burning gas rather than a solid rocket motor in lower-power applications. There are also civil uses for the high-powered generators, particularly in prospecting; you generate an EMP, and monitor its reflections off geological features.
Flux compression generator	Take a copper tube and fill it with precisely-machined explosive; put it inside a helical coil of copper wire. Detonate the explosive to produce a wave travelling along the pipe; the expanding tube short-circuits the windings, compresses the magnetic field within the coil, and produces a substantial pulse (10⁷ amps, 10^-5 seconds, with peak powers of a few terawatts) These are very cheap to build (the Air Force survey cited above suggests a materials-and-labour cost of $2000), though hard to design (you need explosive lenses). They are used to test equipment for EMP compliance, and the Air Force survey suggests very strongly that they've been deployed as weapons.
Pawlowski generator	Take a cylinder, and produce a plasma inside it by some means. Build a coil around it, and use the magnetic field generated to produce a magnetically-loaded plasma. Now collapse the cylinder using explosives. These are not easy to build; only the Russians have so far produced a working model.
Homopolar generator	A compact generator capable of producing direct current in pulses, with 75% efficiency, and capable of being reused. Unfortunately, the device tends to explode if not built to extremely high tolerances.

Effects of EMP

The enormous RF energy produced couples into any metallic conductor, induces huge currents, and destroys transistors and chips. High frequency means best coupling through small holes into small structures; lower frequency couples in large cabling structures. The voltages involved range from.1V to 1kV, and are quite enough to destroy nearby electronics (sometimes to the point of vaporising the tracks off the PCBs)

High-power microwave devices

The above discussion suggests that it's best to use high-frequency weapons. Unfortunately, FCGs work only at low frequencies, so you want to transfer energy from the FCG into the appropriate spectrum. This is done using a vircator (VIRtual CAThode oscillatOR), a device resembling a CRT and producing a circularly-polarised output. See the Air Force survey for more accurate design details.

Before attacking, you should look at the frequencies of radiation the target emits and tune to release energy at those frequencies. Or, better, look at the frequencies it's designed to receive; cellphone towers sound like an almost perfect target in industrialised nations. Some vircator designs allow for chirped pulses, so you can attack on a whole range of frequencies, using the whole output power of the weapon against one frequency at a time.

Protection from electronic attacks

You're unlikely to be a victim soon; these weapons are rare, and it would be hard for a terrorist group to build one. The US is decidedly scared of them, since they make good, cheap weapons of mass destruction - and they don't kill people directly, so military retaliation is harder to justify. Commercial electromagnetic shielding is useful against van Eck devices or nuclear EMPs; it doesn't work so well against higher-frequency attacks.

Commercial power interrupters are pretty much useless, since the rise time of the pulse is shorter than the time the interrupter takes to cut in. However, they defend quite well against the trivial attack produced by activating a stun-gun against the power cable of a computer.