The Rising Drone Threat from Terrorists

Fist-sized craters pockmark 23 Wall Street, the corner building intersecting Wall Street and Broad Street, left by shrapnel from a bomb blast almost one-hundred years ago.¹ On September 16, 1920, a horse-drawn cart parked across from the building that headquartered J. P. Morgan at the time detonated, killing thirty-eight people and injuring several hundred.²

The evolution of vehicular bombs begins with this ruthless feat of ingenuity by a terrorist. Though the New York police never charged anyone, historians suspect that the perpetrator was Mario Buda, an Italian immigrant and anarchist.³

Militants have long sought parity with the artillery of state militaries, but a lack of resources and technological sophistication have posed barriers to radicals determined to inflict mass harm. However, Buda's deadly weapon fashioned out of widely available materials is an example of a practical resolution, which would later be replicated in other vehicle-borne improvised explosive devices (VBIED), leading up to the contemporary use of drones by non-state actors.

Terrorist networks have operated drones since at least 2004, when the Lebanese militant group Hezbollah flew a military-grade drone over Israeli airspace.⁴ However, because of the lack of state support, most terror groups are barred from accessing drone technology of this caliber. Despite this, recent innovation has created an opening for unfettered drone experimentation: hobbyist drones.

Commercial-use drones, the kind available from Amazon.com and the most ubiquitous among militant groups, are not sold with arms or explosives; however, with a little engineering, they can be modified to carry a small payload and strike targets from a distance. Recognizing the potential for terrorism, in 2015, officials from the Department of Homeland Security (DHS), the FAA, and the military held a conference in which videos depicted simulated drone attacks.⁵ DHS again outlined the threat to civilians in a 2017 fact sheet that highlighted the potential for "malicious schemes by terrorists, criminal organizations (including transnational organizations), and lone actors with specific objectives."⁶ It is unclear how many, if any, civilians have been killed by hobbyist drones so far, as terrorist use of drones has occurred outside of the United States. And though the domestic threat might be "imminent," as indicated by FBI Director Christopher Wray, it has not arrived yet. But terrorists are nonetheless becoming frequent drone users, and as non-state groups acquire drones and launch attacks, terrorist drone use has proven destructive on the battlefield.

In this article, I argue that while terrorist drones indeed pose a moderate threat to civilians, non-state use of drones will pose the greatest challenges in combat. Professional militaries will need to invest in conventional air defenses in addition to counter-drone measures, such as electronic jamming, and employ many of the same precautions used to detect and disarm improvised explosive devices (IEDs).

Non-state actors have reached a critical point in the development and use of drones (also known as "unmanned aerial vehicles" or UAVs) in combat and surveillance operations. They are effective drone users, arming drones on their own and executing drone missions that inflict battlefield losses. Additionally, several groups have published drone videos online propagandizing this success, which may encourage lone-wolf drone attacks. Though this unmanned aircraft capability has appropriately stoked terrorism fears, this development echoes previous vehicular technology developments, originating with Buda's bomb.

In this respect, though the potential risk to civilians exists, militants are limited in their capacity to inflict large numbers of casualties by drone.

Militant bomb makers need a vehicle to deliver their explosive devices, requiring terrorists to be creative about moving bombs from Point A to Point B. Suicide vests are a straightforward way to achieve this. However, access to sensitive enemy positions can be limited. In these cases, groups have deployed car bombs, which can inflict heavy casualties, and buried hard-to-detect roadside bombs or IEDs.

Rigged over-the-counter drones pose a new aerial threat to professional militaries because of their ability to surveil battlefield positions, log sensitive information, and launch unpredictable and coordinated attacks. However, as a vehicle for transporting explosives, drones share a...