Terrorist groups across the globe have long had the intent, and in some instances the capability, to use remote-piloted aerial vehicles (drones) in attacks. However, the proliferation of relatively cheap, small, commercially available rotary wing drones has significantly increased the likelihood of drones being used in terrorist attacks, including in the UK.
The well-document use of drones by Daesh in Iraq and Syria, initially for surveillance, targeting and battle damage assessment, and from 2016 onwards, to deliver explosive payloads, demonstrated the potential for such systems to be exploited by terrorists. By 2017/18 Daesh’s use of drones on the battlefield had become extremely sophisticated. Other non-state actors have subsequently adopted the technology for use in combat, and in August 2018, two commercially available quadcopter drones modified to carry improvised explosive devices (IEDs) were used in attempted attack on the Venezuelan President at a military parade in Caracas.
To date, there has been only one case of a terrorist plot to use a drone in the UK (against an Army barracks in Bury[1] in June 2018) and terrorist use of drones remains largely confined to active conflict zones. This is partly due to the continued viability of simpler, lower risk Methodology for causing mass casualties; the primary intent of most Western extremists. A related factor is the difficulty of effectively weaponizing drone technology without relevant material and expertise. Despite this, drones could be employed with little or no modifications to cause public disruptions and spread fear. Therefore, changes in the intent and targeting priorities of malicious actors could result in much greater exploitation of drone technology for terrorist purposes.
The Threat to Aviation
The aviation sector remains a priority target for terrorists, and Islamist extremists in particular. There has been considerable public speculation about the potential for drones to be used to target in-flight commercial aircraft. At present, it is unclear how much of a threat drones pose to civil aviation, or whether terrorists have given serious consideration to using the technology to target aircraft. To date, there have been few verified collisions between airliners and drones, and little testing has been done on the potential effects of collisions or the ingestion of drones by aircraft engines. However, the likely damage of either scenario involving an unmodified drone is not believed to be materially worse than that caused by bird strikes, and it is unlikely to result in the complete loss of an aircraft. However, modified drones potentially pose a greater threat to inflight aircraft. Airliners are most vulnerable to drone strikes while at low altitudes during take-off or landing. Therefore, exposures most at risk from attacks on aviation involving drones are properties in built-up areas below flight paths near airports, including airport terminals and buildings themselves.
More likely than attacks on aircraft hulls is the use of drones to disrupt commercial aviation operations by invading protected airspace around airports; a swarm of drones against an aircraft cannot be discounted. High safety standards and low risk appetites in commercial aviation means safety regulations in the UK and other developed countries prohibits aircraft from flying in airspace where drones have been sighted. Threat actors can exploit this to prevent aircraft operations and cause significant disruption, as demonstrated by events at Gatwick Airport in December 2018. There is potential for non-damage business interruption claims in a similar scenario if it was certified as a terrorist attack. However, the perpetrator would have to be found to have had terrorist motivations. Most proscribed terrorist actors in the UK are currently considered less likely to employ such tactics. However, the use of drones to disrupt commercial aviation would represent a viable Methodology for actors whose main intent is to inflict damage on the UK’s economy, as demonstrated by Extinction Rebellion[2].
Drones as Airborne IEDs
Drones potentially confer numerous advantages to terrorists preparing attacks, including their ability to bypass terrestrial security measures and carry out attacks remotely, thereby reducing the risk of detection and disruption. However, to fully exploit the technology, terrorists must first be able to weaponize drones in their possession. The relatively small size and weight of commercially-available drones restricts their utility as an unmanned firearms platforms or kinetic projectiles. Therefore, in these scenarios, drones are more likely to be used by terrorists to convey either explosive or chemical, biological or radiological (CBR) material to a target.
Explosives
Commercially available drones have been adapted by terrorists for use both as loitering munitions and unmanned aerial combat vehicles. While the transmission of such Methodology from overseas to the UK is a concern, the difficulties in either acquiring off-the-shelf explosives or manufacturing homemade devices mean the likelihood of such tactics being employed in the UK is low. Furthermore, drones are a less reliable delivery mechanism compared to vehicle or person-borne IEDs, and the requisite modifications demand specialist knowledge and material, increasing the risks associated with their use.
The advantages of drone technology to terrorists are less pronounced if the intent is to cause indiscriminate mass casualties. The ubiquity of relatively unprotected crowded places which do not require circumvention of terrestrial security measures means most current UK threat actors will likely forego the complexity of using drone-borne IEDs in favour of simpler, conventional conveyance methods. However, any changes to the targeting priorities of UK-based terrorists could increase the likelihood of drones being used as airborne IEDs.
The relatively small payloads of most commercial drones in the UK also limits their utility as a delivery method; the most popular drones currently sold in the UK have a payload of less than 2kg, while few carry more than 4kg. The Manchester Arena and Parsons Green attacks in 2017 employed IEDs weighing approximately 14kg and 4kg respectively. Therefore, while possible to use currently available drone technology to deliver IEDs, size and destructive power of such devices would be limited, and therefore more suited to targeted attacks than indiscriminate, mass casualty ones.
Drones as Dispersal Method for Chemical, Biological or Radiological (CBR) Agents
The most destructive methodology in the UK would be if a terrorist actor used a drone to disseminate chemical, biological or radiological material. The use of CBR material in any circumstance could cause a significant amount of damage within a very short period of time. This is assessed to be of low probability but with high impact against all target types.
A chemical attack, utilising a drone, in the UK is considered to be possible[3], although manufacturing a military grade CBR device is complex and risky; the use of HAZMAT material is more likely, for example a petrol tanker being hijacked and then set ablaze in a crowded place. Such an incident would cause considerable business interruption and there would likely be a large police cordon erected in all areas deemed to have been affected by the attack. The material or substance would require identification and the subsequent decontamination process could be extensive in terms of time and area. If a drone was used as a delivery method several areas could be contaminated in a short period of time. The small, localised event in Salisbury left some businesses closed for months, and one for over a year.
Mitigating the Risk
Current counter-drone technology can largely be divided into detectors and effectors; the former are designed to detect, track and classify drones, while the latter are intended to bring down hostile drones. Most countermeasures have been designed for the military market and are therefore often unsuitable for use in a civilian environment (due to collateral damage issues). The civilian drone market is also being inundated with new and evolving drone designs and technologies. Therefore, the detector technology needs to continue to adapt at pace to mitigate the full spectrum of threats. Thus, while detecting and countering drones is largely possible with current technology, doing so in a safe, legal and proportionate manner in a domestic setting remains challenging.
Both detectors and effectors have the potential to interfere with electronic and communications systems and technologies (such as mobile phone signals) and must therefore be judiciously used to avoid disrupting many of the systems modern life depends on. This challenge is exacerbated in signal-rich environments like airports. The use of effectors is also problematic; kinetic effectors (e.g. missiles, lasers, firearms etc.) are unsafe to use in built-up areas, and other solutions like jamming carry the risk of targeted drones causing collateral damage when downed. Furthermore, there is currently no legal basis for private bodies to seize or destroy drones operating over private property. Consequently, while detector technology can by employed in the UK by private users with the correct permissions, the use of effectors is currently restricted to law enforcement bodies. Private organizations considering the acquisition of drone countermeasures should ensure that they fully understand procured technology and have the relevant knowledge and permissions necessary for its correct employment.
The relative immaturity of drone technology means that regulatory responses to the threat continue to mature and there is currently no silver bullet in countering them. While wide-ranging restrictions on the use of drones are unlikely, forthcoming regulations aim to ensure drones are only employed by competent users for legal purposes. While unlikely to deter terrorists from acquiring or using drones, this, and the establishment of operating norms and best practices, will enhance the ability of authorities to differentiate the malicious use of drones from legal, largely recreational activity. Equally, improved recording and reporting of incidents will provide a better understanding of the threat and help inform the development of incident response guidance. Other potential regulatory responses include mandating the incorporation of safety features such as geo-fencing (the establishment of virtual boundaries for geographic areas, the transgression of which would override the commands of the drone operator) into commercially available drones. Although such measures could be circumvented by more sophisticated terrorists with the requisite knowledge, it would make the malicious use of drones more difficult.
For most businesses, investment in specific counter-drone technology is unnecessary, with resources better committed to improving awareness of the threat, and developing procedures for identifying, reporting and responding to drone sightings. Understanding the implications of trying to impose post incident cordons on something which you cant see should also be considered by security directors and risk managers.
[1] https://www.bbc.co.uk/news/uk-england-manchester-49645627
[2] https://www.hstoday.us/subject-matter-areas/terrorism-study/terrorists-use-of-drones-promises-to-extend-beyond-caliphate-battles/
[3] https://uk.reuters.com/article/uk-britain-security/possibility-of-chemical-attack-in-uk-getting-closer-security-minister-idUKKCN1MJ1HW