Electromagnetic terrorism: protection and counteraction.

UKOV Vyacheslav Sergeevich, Candidate of Technical Sciences

Analysis of security system development trends shows that the most effective in terms of the “efficiency quality” criterion are integrated security systems (ISS), the core of which is a personal computer [1]. However, the practice of operating ISS shows that these systems, unfortunately, also have their weak points, knowledge of which will certainly help the user eliminate the shortcomings and improve the operational, technical and operational characteristics of existing ISS. This primarily applies to methods of protection against Force Destructive Impact(SDV) – a sharp surge in voltage in power supply networks, communications or signaling of security systems with the amplitude, duration and energy of the surge, capable of leading to failures in the operation of equipment or to its complete degradation. In this article, using the example of the ISB, modern possibilities of protection against destructive force impact, both intentional and spontaneous, are considered.

Technical means of destructive force impact (TMFDI) are, in essence, electromagnetic weapons that are capable of remotely and silently striking, for example, any unprotected security system. The main thing is to ensure the appropriate power of the electromagnetic pulse. The secrecy of the attack is significantly increased by the fact that the analysis of damage to the destroyed equipment does not allow for the unambiguous identification of the cause of the damage, since the cause may be either intentional (attack) or unintentional (for example, induction from lightning) destructive force impact. This circumstance allows the attacker to successfully use TMFDI repeatedly.

Main channels of destructive force impact

The analysis shows that a computer or any other electronic equipment of the security system, taking into account the environment of energy transmission, can be subjected to degradation by SDV through three main channels of destructive force impact (FDI):

• through the power supply network (FDI No. 1);
• through wire lines (FDI No. 2);
• through the air using powerful short electromagnetic pulses (FDI No. 3).

The main channels of destructive impact on the integrated security system and defense lines are shown in Fig. 1.

Fig. 1. Main channels of destructive force impact
on the integrated security system of the facility

As can be seen from Fig. 1, the use of SDV, in principle, allows to overcome all standard defense lines in the ISS. Everything is determined by the power of impact, the selected means of protection, the available financial capabilities. These circumstances determine the choice of defense strategy. Let's consider one of them — a two-level defense strategy (TLDS).

The first (internal) level of the DSS involves selecting the appropriate technical means and constantly testing their stability for compliance with regulatory documents (Table 1). The second (external) level involves organizational and technical measures aimed at the maximum possible weakening or blocking of signals from the VLF (in particular, through shielding).

Table 1. Main regulatory documents on testing the immunity of technical equipment to electromagnetic influences

The main organizational and technical recommendations for protecting security systems from SDV are given in Table 2.

Table 2. General organizational and technical measures for protecting against SDV

Force destructive impact on the power supply network

To implement the SDV over power supply networks, special technical means are used that are connected to the network directly using galvanic coupling through a capacitor or using inductive coupling through a transformer. Experts' forecasts show that the probability of using SDV is growing year by year. Therefore, when developing a facility security concept, it is necessary to take into account the possibility of SDV over power supply networks, for which, first of all, it is necessary to classify the technical means of SDV. However, given the specific purpose of these means and the reluctance of the companies that produce them to widely advertise their work, the classification task turned out to be non-trivial. A possible classification of modern technical means of SDV over power supply networks, carried out based on the analysis results, is shown in Fig. 2.

Fig. 2. Classification of technical means of the SDV by power supply networks

The presented classification is quite clear and does not require additional explanations, with the exception, perhaps, of the class “Special and other TS SDV”. This class includes, in particular, various surrogate TS SDV, available at hand. For example, the nearest transformer substation can be used as a technical means of influence, to the part of the secondary winding of which it is possible to connect a TS SDV with a capacitive storage device, the parameters of which are selected so that the secondary winding of the transformer, the magnetic circuit and the capacitive storage device form a step-up resonant autotransformer. Such a force impact can disable all electronic equipment serviced by this substation. This class also includes means of reprogramming uninterruptible power supplies (UPS) using, for example, software bookmarks. Such a bookmark can be activated by the appropriate command on the power supply network to briefly reprogram the UPS to the maximum possible output voltage, which will also lead to failure of the electronic equipment connected to it.

As an example of the high efficiency of the destructive impact of the TS SDV, we can note relatively inexpensive devices with electrolytic capacitors, having a specific volumetric energy equal to 2000 kJ/m3. Such a device, placed in a regular case, is capable of disabling up to 20 computers simultaneously. The estimated cost of such a case is from 10,000 to 15,000 US dollars. Even more effective are molecular accumulators (ionistors), the specific volumetric energy of which reaches 10 MJ/m3. The TS SDV, containing ionistors, is already capable of disabling all computers of a large computing center. The cost of such a technical device is approximately 50,000 US dollars (the cost and energy parameters of the TS SDV are given to assess the effectiveness of protection).

Recently, a large number of technical means have appeared on the security market that are capable of not only detecting suspicious equipment, but also destroying it if necessary. A striking example of such technical means is the product of the French company “Cofroexport S.A.”, specializing in the field of security and radio communications, in particular, the so-called radio bug detection suitcase, which ensures disablingelectronic means by connecting to a higher voltage line.

Currently, there are two main channels for the penetration of SDV energy through the power supply network:

• conductive path through the secondary power source (SPS);
• interference through parasitic capacitive and inductive connections, both internal and external (for example, through signal circuits and communication lines), and, according to the features of the circuitry, the channels of influence can be either symmetrical or asymmetrical.

As an example, we will assess the stability of the components of the main power supply element of the integrated security system – the secondary power source, the typical circuit diagram of which is shown in Fig. 3, and the results of the stability assessment of the elements of the typical secondary power source unit are in Table 3.

Fig. 3. Schematic diagram of a typical secondary power supply unit

Table 3. Results of assessing the resistance of VIP elements to the effects of SDV

As can be seen from the table, the elements of the input LC filter have a very low energy absorption capacity and do not provide protection against powerful impulse interference. Therefore, if the LC filter is the only protection device at the input of the VIP, then the TS SDV to achieve the goal is sufficient to provide the ability to supply powerful impulse interference with an amplitude of 2 kV and an energy of 1-2 J with a sufficiently steep front.

In modern VIPS, the main protection functions against powerful interference are performed by a varistor. However, despite the high levels of operating currents, they have a maximum permissible dissipated power of units of watts, so when exposed to long pulses with a relatively small current, they fail, causing the fuse at the input to burn out. In this case, the TS SDV requires energy of 50-100 J, amplitude — 1 kV, pulse duration — 0.1 s.

To disable the capacitors of the inverter input filter and the diodes of the TS SDV bridge, significantly less energy is required, and to bypass the varistor protection, the difference in the breakdown voltage of the capacitors and the voltage of the effective voltage limitation of the varistor is used, which is 70-120 V. The problem of force action is solved by using pulses with a duration of up to 5 ms, an amplitude of 500-600 V and an energy of 15-25 J. In this case, after the breakdown of the capacitors, an additional current pulse occurs through the bridge diodes, which for a hot thermistor reaches 1000 A, which disables the diodes. With such an impact, it is very likely that transistors and other elements of the inverter will fail, as well as destructive pulses will pass to the VIP output, which will damage other components of the security system.

It is especially necessary to note the possibility of a powerful destructive force impact using interference through parasitic capacitances between the elements and nodes of the circuit. It has been established that the input high-voltage and output low-voltage circuits of VIP equipment (for example, computers) have a capacitive coupling through a parasitic capacitance equal to 10-30 pF, and a parasitic capacitance equal to 5-10 pF connects the power supply network with the elements of the computer motherboard. Through these parasitic capacitances, it is possible to completely block the operation of software and hardware by generating high-voltage pulses with a nanosecond rise time in the SDV TS, including ensuring data distortion, computer freezing and software failures. These destructive impact capabilities impose additional requirements for protection against impulse interference.

Based on the analysis results, it can be concluded that traditional VIPs are insufficient to protect computers and security equipment from SDV. However, as a rule, an additional protection device (UPS, stabilizer, filter, network conditioner, etc.) is installed between the power grid and VIP, which must also be taken into account when assessing resistance to SDV. Uninterruptible Power Supply (UPS) have recently become especially widely used in security systems, and we should dwell on them in particular. These devices are designed to improve the quality of AC power and ensure uninterruptible power supply to equipment in the event of a power grid failure.

By control method, UPS are divided into OFF-LINE and ON-LINE types. The main difference is the choice of the main channel for transmitting energy to the consumer.

For OFF-LINE mode in the main mode, the channel switch connects the UPS input to the output through a branch containing only the input filter. In this case, the batteries are recharged from a low-power charger, and the voltage from the inverter does not go to the source output. In the battery support mode, when the input voltage deviates from the permissible limits or disappears, the channel switch connects the branch containing the inverter, and energy is supplied to the consumer from the batteries.

ON-LINE mode is characterized by constant switching on of the branch containing a powerful charger, battery and inverter to the output of the UPS unit. Such a scheme allows not only to eliminate switching time, but also to provide galvanic isolation of the input-output, to have a stable sinusoidal output voltage. In case of failure of any cascade in the direct branch of energy transfer, overloads, as well as when the batteries are discharged, the channel switch connects the branch connecting the input-output through the filter. This auxiliary path of energy transfer, called bypass (BY PASS), is of particular importance in case of SDV and allows to bypass the UPS protection to defeat more important units of the security system, for example, a computer.

Recently, line interactive UPS have appeared, which are a further development of off-line technology. They are distinguished by the presence of a stabilizing autotransformer at the input, which helps to stabilize the output voltage of the UPS. In some cases, if power interruptions of several milliseconds are acceptable, line-interactive UPS are preferable to off-line type and cheaper than on-line devices.

Usually, when the SDV is detected in the power supply network, the UPS fails, and in this case the bypass is activated and through it the energy of the SDV TS reaches the target bypassing the UPS. In addition, as a rule, in thyristor stabilizers, voltage correctors, and network switches, when the SDV is detected, spontaneous “unlocking of thyristors” occurs contrary to the standard algorithm of the control circuit with an emergency shutdown or failure. Thus, traditional power protection devices not only do not protect security systems from SDV, but are themselves highly susceptible to destructive effects. The main recommendations for protecting security systems from SDV in the power supply network are given in Table. 4.

Table 4. Protection of security systems from SDV via the power supply network

Force destructive impact on low-current wire circuits

For the penetration of the energy of the LWF through wire lines, it is necessary to overcome the maximum absorption capacity of the components that can be used in the input circuits. Analysis shows that for the degradation of these components (microcircuits, transistors, diodes, etc.), the impact of a pulse with an energy of 1 1000 μJ is sufficient, and this pulse can be very short, since the breakdown time of a MOS structure or pn junction is 10 — 1000 ns. As is known, the breakdown voltages of junctions are from units to tens of volts. Thus, for gallium arsenide devices, this voltage is 10 V, memory devices have threshold voltages of about 7 V, logic integrated circuits (IC) on MOS structures — from 7 to 15 V. And even silicon high-current bipolar transistors, which have increased resistance to overloads, have a breakdown voltage in the range from 15 to 65 V. From this we can conclude that for VDV via wire channels, the energy required is several orders of magnitude lower than via the power supply network, and the destructive effect can be implemented using relatively simple technical means that ensure a high probability of disabling the target of attack. In particular, in this case, any electromagnetic shocker can be used for VDV.

Further analysis should be carried out taking into account the presence of impulse interference protection devices at the input. In this case, the protected components have a significantly higher maximum energy absorption capacity (up to 1–10 J for low-speed devices and up to 1–10 mJ for high-speed devices). However, due to high prices, high-quality protection devices have not yet found wide application in Russia. The classification of SDV TS by wire lines is shown in Fig. 4.

Fig. 4. Classification of low-current devices by wired low-current lines

The main recommendations for protecting security systems from low-current devices via wired lines are given in Table 5.

Table 5. Protecting a security system from low-current devices via wired lines

Wireless destructive force impact

The most hidden and most effective is the channel of forceful destructive action via the ether using a powerful short electromagnetic pulse. In this case, it became possible to implement fairly compact electromagnetic technical means of the VLF, placed outside the object of attack and at a sufficient distance from communications to mask the attack. The design of the electromagnetic TS VLF using the example of a generator with a virtual cathode (vircator) is shown in Fig. 5.

Fig. 5. Design of high-frequency electromagnetic TS SDV

As can be seen from Fig. 5, the design of the vircator is quite simple. Its operating principle can be described just as simply. When a positive potential of about 105 – 106 V is applied to the anode, a flow of electrons rushes from the cathode to the anode due to explosive emission. After passing through the anode grid, it begins to slow down due to its own “Coulomb field”. This field reflects the electron flow back to the anode, forming a virtual cathode. After passing through the anode in the opposite direction, the electron flow slows down again at the surface of the real cathode. As a result of such interaction, a cloud of electrons is formed, oscillating between the virtual and real cathodes. The microwave field formed at the oscillation frequency of the electron cloud is radiated by the antenna through the fairing into space. The currents in the vircators, at which generation occurs, are 1 – 10 kA. Experimentally, powers from 170 kW to 40 GW in the centimeter and decimeter ranges have already been obtained from vircators.

The injection of a powerful electromagnetic pulse in such a VLF TS is carried out using a special antenna system, the efficiency of which largely determines the operational and technical characteristics of the entire VLF complex. Despite the presence of a directional antenna, a powerful electromagnetic signal (EMS) affects all components within the electromagnetic impact zone and all circuits formed by connections between equipment elements when attacking an object, therefore, not being a means of selective impact, VLF TS inflict global damage, justifying the established concept of an “electromagnetic bomb”.

The urgency of the problem of protection against electromagnetic VHF increases also because at present some research works have ended with the development of prototypes of information weapons. Thus, of interest is the American prototype of this class of weapons under the conditional name MPS-II, which is a high-power microwave radiation generator using a mirror antenna with a diameter of 3 m. This prototype develops a pulse power of about 1 GW (voltage 265 kV, current 3.5 kA) and has great capabilities for waging information warfare. Thus, in the manual for its use and technical maintenance, its main characteristic is defined: the defeat zone is 800 m from the device in a sector of 24 degrees [2]. Moreover, it is important to note that people with electronic heart pacemakers are prohibited from accessing the device. Using this device, you can effectively erase not only credit cards, but also records on magnetic media.

The use of new technologies, in particular, phased antenna arrays, allows for the implementation of VLF on several targets at once. An example is the GEM2 system, developed by order of Boeing by the South African company PCI, which consists of 144 solid-state emitters of pulses with a duration of less than 1 ns with a total power of 1 GW. This system can be installed on mobile objects. Even the examples considered indicate the great possibilities and high efficiency of the new information weapon, which must be taken into account when ensuring the protection of information, especially since the combat use of such weapons in a missile version was already recorded during the Gulf War.

The analysis shows that the most dangerous TS VLF for integrated security systems are technical means of destructive force action via the air using an electromagnetic pulse (wireless TS VLF). This is especially true for powerful mobile TS VLF, the destructive action of which can be carried out from an unguarded area. Unfortunately, the lack of open information on this type of TS VLF significantly complicates their classification. The classification of wireless TS VLF used in this work is shown in Fig. 6.

Fig. 6. Classification of VLF TS by ether (wireless VLF TS)

When analyzing the possibilities of using VLF TS, it should be noted that the most convenient to use and the most advanced in research are high-frequency electromagnetic VLF devices, including magnetrons, klystrons, gyrotrons, free-electron lasers, plasma-beam generators, as well as the vircators discussed above, which, although they have low efficiency (units of percent), are the easiest to tune in frequency. Plasma-beam generators are the most broadband, and the peculiarity of gyrotrons is that they operate in the millimeter range with high efficiency (tens of percent).

However, one of the first examples of electromagnetic weapons, which was demonstrated back in the late 1950s at the Los Alamos National Laboratory in the United States, was a generator with explosive compression of a magnetic field [3].

Subsequently, many modifications of such a generator were developed and tested, for example, in the USA, developing an impact energy of tens of megajoules, and the peak power level reached tens of terawatts, and the current produced by the generator was 10 — 1000 times greater than the current generated by a lightning discharge [4]. At present, some of these models have already been adopted for service and have been successfully tested in the Persian Gulf, Yugoslavia, etc. Unfortunately, there have been many examples of how military equipment becomes the property of terrorists after some time. This happens especially often with technical means of the tactical level (low-power means). And you should not wait for the «thunder to strike». Despite the fact that statistics on the use of VDV are not kept today (as a rule, incidents are attributed to natural disasters such as thunderstorms, static, random coincidences, etc., and it is very difficult to identify them), the probability of using VDV today is very high. Therefore, the problem of protection from electromagnetic VLF, being very relevant, requires its solution. The main recommendations for protecting security systems from electromagnetic VLF via the air are given in Table 6.

Table 6. Protection of security systems from electromagnetic VLF via the air

More detailed information on protection against ET can be found in the literature provided and on Internet sites.

Thus, destructive force impact, implemented via wired and wireless channels, as well as via power supply networks, is currently a serious weapon against object protection systems, in particular, integrated security systems and protected premises. This weapon justifies its name «electromagnetic bomb» and is more formidable in terms of its effectiveness than software destructive weapons for computer networks. Analytical studies show that new technologies make technical means of destructive force impact increasingly promising for use and require more attention, primarily from security services and developers of protection systems. By the way, not only equipment but also people suffer from SDV. But this is another, no less urgent problem, which you will read about in the next issues of the magazine.

Literature

1. Ukov V.S. Security: technologies, means, services. — M.: KUDITS — IMAGE, 2001.
2. Winn Schwartau. More about HERP than some? — Information Warfare: Thunder’s month press, New York, 1996.
3. Carlo Kopp. The E-bomb — a Weapon of Electronical Mass Destruction. — Information Warfare: Thunder’s month press, New York, 1996.
4. David A. Fulghum. Microwave Weapons Await a Future War. — Aviation Week and Space Technology, June 7, 1999.