Discussion on the disposal and prevention of mail bombs

Song Tingjia, Chen Shie

【Abstract】Mailing bombs are a common explosive crime method frequently employed by criminals, characterized by their good concealment, strong targeting, high accuracy, proximity of explosion, and significant harm. Public security and armed police forces are crucial in counter-terrorism and anti-explosion efforts. It is essential to prepare in advance, enhance research on the characteristics of mail bombs and their handling strategies, continuously improve practical handling capabilities for explosive devices, and lay a solid foundation for taking the initiative in maintaining stability and security.

【Keywords】Mail Bomb | Explosive Attack | Case Study

From December 1 to December 10, the embassies of the United States, Ukraine, and other countries in Spain received a total of 13 mail bombs. One of these, addressed to the Ukrainian ambassador in Spain, exploded during handling, causing hand injuries and a concussion to a security personnel. On December 10, an assistant to the Commander-in-Chief of the Ukrainian Armed Forces was killed at home when a mail bomb disguised as a birthday gift exploded while he was showing it off. The series of mail bomb attacks could potentially trigger a "broken window" effect and a "butterfly effect," posing significant uncertainties to the social stability of various countries. As crucial forces in maintaining national security and stability, public security and armed police units should prepare in advance, strengthen research on the characteristics of mail bombs and their handling strategies, enhance practical capabilities in dealing with explosive devices, and have a profound and positive significance in winning the initiative in maintaining stability and security.

I. Structure and Characteristics of Email Bombs

Mail bombs typically refer to terrorists concealing explosives in letters, books, magazines, or packages, using methods such as mailing, express delivery, carrying, or switching to deliver the explosive devices to the intended targets or destinations, aiming to carry out attacks or create social panic. These are usually divided into two types: one is mailed in the form of a letter, which contains a smaller amount of explosive material. The other is disguised as an express package, containing an explosive device, with the amount of explosive material generally determined by the size of the package.

(I) The Structure of Mail Bombs

As an explosive device, the mail bomb generally consists of explosives, electric detonators, initiating devices (wires, power sources, initiating mechanisms), and outer packaging. Based on actual cases, three main types have been identified.

One is to use birthday cards or greeting cards as a cover. When the victim receives such a letter and tears open the envelope to open the birthday card, the card explodes. The basic principle of the circuit for detonating this type of bomb is a break-type circuit. An appropriately sized insulating strip is set between two contact points, and the contact points are attached to one side of the card, book, or magazine along with other components (explosives, power source, detonator, etc.). One end of the insulating strip is inserted between the two contact points, while the other end is glued to the other side of the card or book. Normally, when the card or book is closed, the insulating strip is between the two contact points, causing the circuit to be open and preventing an explosion. When the card or book is opened, the connected insulating strip is pulled out, bringing the two contact points into contact, completing the circuit, and triggering the bomb.

The second method involves mailing a letter, where upon receiving the letter and tearing open the envelope, an explosion occurs. The circuit principle of this bomb detonation is basically the same as mentioned above, but with better technical execution. The two contact points are typically composed of two very thin electrode sheets, separated by an insulating strip of moderate length and good flexibility. When the envelope is torn open, the insulating strip is pulled apart, causing the two electrode sheets to touch, completing the circuit and triggering the explosion.

The third type is a larger parcel bomb, which has a more complex detonation principle and higher technical content compared to the previous two types of mail bombs. The outer packaging is varied, with more explosive charge and more camouflage items inside the box, making it more difficult to handle.

(2) Main Characteristics of Email Bombs

First, precise delivery and remote detonation. Mail bombs are usually not large and are typically delivered to the target through mail or package delivery services. The attacker can strike the target from a great distance. Second, strong concealment and difficult identification. Mail bombs generally use electric detonation devices. With the advancement of technology, the integration level of detonation devices and the manufacturing technology of explosives have continuously improved, significantly enhancing the concealment of mail bombs, making them easily evade general-level security checks. Third, good damage effect and significant harm. Mail bombs are usually detonated at close range, causing maximum damage to the target. The consequences of such attacks easily attract social attention and cause panic.

II. Basic Characteristics and Detection Methods of Email Bombs

(1) Basic Characteristics of Email Bombs

1. Thick and heavy. To place detonators, power sources, wires, and explosives into a small parcel and disguise it, the parcel needs to have a certain thickness and avoid accidental detonation during mailing. Typically, books or magazines are sealed and glued at both ends, making the weight heavier than a normal mail. 2. Hard texture, resistant to folding. Terrorists usually secure various components and explosives on a hard medium to ensure safety when making mail bombs, making the mail less prone to folding. 3. When touched, the mail may feel like it contains something unusual that is not found in normal mail. 4. The exterior of the mail may have residues from the manufacturing of the explosive device, such as oily substances, white powder, yellow powder, or black powder. 5. Excessive postage. Criminals often overpay postage or add insurance fees to ensure the bomb reaches the intended recipient. 6. Some stamps or labels are placed in inappropriate locations. Criminals often leave small traces on envelopes or packages while making bombs, and then cover them with stamps or labels. 7. To avoid being traced after the crime, criminals usually do not clearly write the sender's address. To avoid revealing their identity through handwriting, they sometimes cut out printed letters from newspapers or magazines to form the address. 8. Odor detection may reveal unusual smells. For example, the letter might smell of bitter almonds; if it contains black powder, it might smell like rotten eggs. 9. Criminals often install a safety mechanism (safety switch) to prevent accidents during the manufacturing process. After assembling the bomb, the safety mechanism needs to be opened from the outside, sometimes leaving small holes on the envelope or packaging.

(II) Detection of Email Bombs

The detection methods for mail bombs typically involve a combination of visual judgment and instrument-based detection.

Intuitive Judgment Method

The intuitive judgment method involves using one's senses in combination with relevant professional theoretical knowledge, and making a direct judgment on whether a letter contains an explosive device through mental assessment. This method typically includes two approaches: visual identification and odor identification. Visual identification primarily involves four basic methods: looking, listening, touching, and weighing. First, observe the surface of the mail for any suspicious features; second, listen in a quiet environment to detect any unusual sounds within the letter; third, feel the letter through touch to determine if it contains a hidden explosive device; fourth, weigh the letter to check for any abnormal weight. Odor identification involves smelling the scent emitted from the mail and determining if it matches the normal scent of a regular mail package.

Instrument Detection Method

Instrument detection methods typically include metal detector detection, electronic listening device detection, radiographic inspection, compound security scanner detection, explosive detector detection, non-linear junction detector detection, and borescope inspection.

①Metal Detector Inspection Method. Using a metal detector to scan and inspect letters can detect the presence of metal items or components within the letter. Combined with other instruments for detection, it can determine whether there is an explosive device concealed inside the letter.

②Radiographic Inspection Method. The radiographic inspection system is one of the main devices for security checks and is widely used in the field of anti-explosive security. X-rays are a type of electromagnetic wave with extremely high frequency, extremely short wavelength, and immense energy, with wavelengths ranging between -. X-rays can be used to detect objects primarily because of their strong penetrating ability, meaning they can pass through objects; secondly, their fluorescence effect, where X-rays can cause fluorescent substances to emit light; and thirdly, their ability to expose photographic film. These three properties are crucial for X-ray detection of objects. In practice, it has been found that when X-rays pass through different materials, due to varying structures and densities, the degree of absorption of the X-rays also differs. This means the amount of X-rays passing through different objects varies, resulting in images with different color contrasts on the fluorescent screen or photographic film, achieving the purpose of detecting objects. It has been determined that when using large handheld X-ray inspection devices (where the emitter and collector are not in the same machine and the imaging area is greater than square centimeters), there is generally a blind area of about - centimeters at the bottom of the collector, requiring small parcels to be elevated before shooting. Alternatively, direct scanning X-ray inspection devices (where the light source and collector are integrated into one machine) can be used to directly scan and detect letters.

③Electronic Listening Device Detection Method. The electronic listening device, also known as a time bomb detector, can detect whether there is a mechanical timing explosive device hidden inside a letter. Practice has proven that it can also detect the presence of electronic timing devices within objects. This method is generally used in quiet environments and requires the equipment's sensitivity and other parameter performance to be properly adjusted before use.

④Nonlinear Junction Detector Method. The nonlinear junction detector, by emitting and receiving second and third harmonics, can detect whether there are junctions or pseudo-junctions inside the package, thereby determining if there are explosive devices using electrical detonation, such as wireless remote control explosive devices, electronic timing explosive devices, and electronic induction explosive devices.

⑤ Explosive Detector Detection Method. Explosive detectors, through swab sampling analysis or air sampling analysis, can analyze and determine whether the mail contains explosive components.

⑥Composite Security Scanner Detection Method. The composite security scanner combines the functions of an electronic listening device and a non-linear node detector, capable of detecting the presence of timing explosive devices or other electrically initiated explosive devices within packages.

⑦ Flexible Endoscope Inspection Method. Using flexible endoscopes to inspect the interiors of letters and packages for hidden explosive devices. However, there is a risk if the package contains light-sensitive devices.

III. Elimination of Email Bombs

When dealing with mail bombs, the method of disposal should be determined based on the environment and the duration of the situation. It is usually handled by professionals, and there are generally four methods: transfer and destruction, decomposition using an explosive device disassembler, decomposition by gunfire, and manual disassembly.

(1) Transfer and Destruction Method

When a mail bomb is located in a critical area and there is no certainty in rendering it ineffective, the explosive device should be transferred to a safe location before attempting to render it ineffective or destroy it. Common methods include: manual transfer, transfer by bomb disposal manipulator, transfer by rope and hook team, and transfer by robot.

(II) Explosive Disintegrator Decomposition Method

The Explosive Disruptor, commonly known as the Water Cannon Gun, is a demining equipment used for dismantling and destroying explosive devices. It can destroy explosive devices with high danger levels and trigger or sensor-initiated detonation methods on-site, making it the most commonly used and reliable method for dismantling explosive devices. This method is typically employed when the mail bomb has a smaller quantity of explosives and after an assessment of the surrounding environment permits its use.

(III) Decomposition Method of Gunfire

When the internal structure of a mail bomb has been identified, a high-precision sniper rifle can be used to shoot at the bomb's battery, explosive, or detonator from a distance, thereby achieving the purpose of rendering it ineffective and decomposing it.

(IV) Liquid Nitrogen Immersion Method

Utilizing the ultra-low temperature characteristics of liquid nitrogen (boiling point -196℃), deep freezing the explosive device can cause the explosive charge to lose its explosive performance or reduce its power, render the electrical initiation system's power source ineffective, and stop the mechanical moving parts. Freezing the explosive device can be achieved through two methods: immersion or spray.

(V) Manual Demolition Method

Manual disassembly of mail (parcel) bombs should be conducted under proper protection and ensuring safety. Identify the wiring method of the explosive device through X-ray imaging or by tactile inspection (of letters or cards), determine the type of device, and for different types of devices, the position for cutting the wires varies.

Single power source, single initiation device. This type of device is relatively simple; cut the wire near the power source or initiation component (such as a detonator).

( ) Single power supply, composite initiation device, should cut the wire near the power source.

Dual power supply, single detonator, the wire should be cut near the detonating element.

When encountering a dual power supply or a composite detonation device, you can sequentially test and disconnect the two power supplies, or disconnect all the composite detonation components. Alternatively, you can use a wire cutter to simultaneously cut the power supply wires.

After cutting the wires as described above, if the circuit contains a capacitor, the wires connecting both ends of the capacitor should be cut to prevent the capacitor from discharging and causing the bomb to explode.

The location of the anti-detonator device has been clearly identified, and the wires at both ends can be cut to render the detonation contact point inoperative, followed by the separation of the explosives, detonators, and power sources.

For the disarming method of small-sized mail bombs, one can first analyze and observe to determine the position of the wires to be cut. Then, place the mail into a transparent folder with an open window on one side, securing it tightly so that the area to be cut is exposed through the window. Use a sharp knife to gently cut away the outer packaging, revealing the inner wires. Use scissors to cut the wires, and after confirming that there are no errors, proceed to open the mail. When using this method, it is important to note:

Manual disassembly of email bombs should ideally be performed by professionals who have received specialized training.

Strictly enforce the one-person operation rule. Before dismantling, release body static electricity. If possible, wear a bomb disposal suit, helmet, and face shield.

When cutting the outer packaging, handle it gently and try not to touch the internal connections. When cutting the wires, aim to cut and tie them individually.

Without ensuring complete disassembly, the email must not be opened to prevent accidental detonation.

IV. A Brief Discussion on Several Measures for Preventing Mail Bomb Threats

(1) Strengthen intelligence information sharing

The armed police forces, public security organs, and other national anti-terrorism and anti-explosion departments should strengthen intelligence collection and analysis in peacetime, comprehensively grasp the data and information of key individuals involved in terrorism, and establish and improve anti-terrorism information databases; take the lead in organizing emergency rescue, explosive-proof security checks, express logistics, and other departments to hold intelligence information consultations, timely report the whereabouts and movements of key individuals involved in terrorism, and guide explosive-proof security checks and logistics companies to intensify security checks on express and logistics shipments from these key individuals in a targeted manner.

(II) Establish and improve relevant plans and contingency plans

With the people's safety as the primary concern, establish emergency response plans and disposal procedures for preventing attacks using various non-standard explosive devices; in daily work, conduct thorough drills of these plans to enhance the coordination and cooperation among units in handling explosive attacks, dynamically identify deficiencies in the plans, and continuously improve and refine them.

(III) Enhancing Awareness of Prevention and Training in Anti-Explosion Skills

The primary purpose of explosive attacks is to cause casualties and panic. By enhancing awareness of prevention and mastering relevant anti-explosion skills, the intentions of terrorists can be thwarted, ensuring the safety of people's lives, and enabling effective handling when explosive devices are discovered.

(IV) Strengthen the construction of new anti-explosion equipment

With the development and popularization of science and technology, improvised explosive devices are also evolving towards modernization and intelligence, inadvertently increasing the danger and technicality of search and disposal operations. While fully utilizing and leveraging the existing search and disposal technology and equipment, we must, in light of the changes in our adversaries and the battlefield under the new circumstances, increase the research and utilization of unmanned and intelligent equipment to ensure safe and efficient handling of any mission.

V. Conclusion

Mailing bombs are a common explosive crime method frequently employed by criminals, characterized by precise delivery, remote detonation; strong concealment, difficult to identify; good damage effect, and significant harm. They pose a great threat to the security and stability of our country and the world, necessitating research and preparation. The detection methods for mail bombs typically combine visual judgment with instrument detection. When dealing with mail bombs, there are generally four methods: transfer and destruction, decomposition with an explosive disassembler, decomposition by shooting, and manual removal. Mail bombs can generally be mitigated through methods such as strengthening intelligence information sharing, establishing and improving relevant plans and scenarios, enhancing awareness and training in prevention and bomb disposal skills, and strengthening the construction of new bomb disposal equipment.

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