Q. Could terrorists carry out a strike with drones?
On the one hand, lone-wolf terrorists already have a number of tools at their disposal for killing large numbers of individuals, including the rudimentary but quite lethal AK-47 that the alleged terrorist on the high-speed train from Amsterdam to Paris had planned to use to kill scores of people in a 2015 episode. These weapons are already available and can potentially be devastating. On the other hand, drones may be the perfect tools for terrorists. There are several features of drones that could make them conducive to terrorism.29
First, they offer flexibility in terms of launch sites, since small drones can be launched even by hand, which means they do not require sophisticated ground stations. Similarly, their ability to loiter and wait for the appropriate time to strike offers strategic value in terms of maximizing damage, essentially acting as airborne improvised explosive devices (IEDs) that can seek out specific high-value targets instead of hoping those targets will be in proximity to a stationary explosive device.30 Senator Dianne Feinstein (D-CA) believes that, "in some respects, it's a perfect assassination weapon. It can see from 17,000 to 20,000 ft. up in the air, it is very precise, it can knock out a room in a building if it's armed, it's a very dangerous weapon."31 Even low-cost drones could be used in a kamikaze style to target an individual or, if equipped with a biological or a chemical agent, be quite disruptive.
Second, many air defense systems that could target larger aircraft are likely to be unsuccessful against smaller drones. A good example is a North Korean spy drone, which has a 5- to 6-foot wingspan and whose wreckage has been found repeatedly in South Korea. Analysis of the wreckage suggested that drones had been able to cross into South Korean airspace for a one-year time period, and revealed camera equipment that had collected images of the Demilitarized Zone and the South Korean president's office and residence. While these quite rudimentary drones were fairly benign because of their low payloads, one concern is whether they could be reconfigured to carry nuclear or chemical devices. Moreover, the act of penetrating South Korean air defenses points to how these drones could be used in larger numbers to swarm across the border and do considerable collective impact. As defense analyst Van Jackson put it in Foreign Policy, "it's the low-performance qualities of North Korea's drones that enable them to evade South Korean defenses, which are optimized for more traditional threats from bigger, faster, higher-altitude aircraft."32
Third, while these small drones might not be a weapon of mass destruction, they would certainly have an important psychological impact, along the lines of a terrorist attack that serves to unnerve the population. Indeed, in the case of the North Korean drone, the fact that even a small system could penetrate air defenses multiple times jarred the population. One Air Force colonel in Korea explained that this threat by North Korea took on high political salience for South Korean politicians who were trying to cultivate images as leaders who were attentive to the populace's security concerns. The idea of terrorism is to create psychological anxiety and in this sense even a hobbyist drone, despite its seemingly harmless design could terrorize a population whether unarmed or mounted with small amounts of a chemical or biological weapon.
Lastly, since individuals can buy personal drones inexpensively and easily online, the issue of ownership and attribution could be extremely difficult, making retaliation difficult and therefore doing little to deter an attack in the first place. Drone owners had not been required to register their aircraft, which made the issue of attribution—and retaliation and deterrence—virtually impossible. Even once the government requires registration, individuals could assemble their own drones that are not only not registered but also not bound by the type of "geofencing" that manufacturers have placed on some drones to prevent the drone from going near airports, for example. States could also plausibly deny involvement in a drone-related terrorist incident given that there would be no pilot implicated and the type of drone used might well not bear any markings or radio signature that identifies the sponsor. Thus, the factors that might deter individuals or groups from carrying out an attack—retaliation—might not be operative for drones.
Nonetheless, even state-sponsored terrorist groups are likely to find drones to have somewhat limited utility in a more conventional setting. The group Hezbollah has been sending drones into Israeli airspace for about a decade now but with limited success. In November 2004, Hezbollah piloted a drone into Israeli airspace, hovering over and observing the town of Nahariya for roughly 20 minutes before returning to its launch site in Lebanon. The next two attempts to send drones into
Israel, in April 2005 and August 2006, were intercepted by the Israeli military. Hezbollah stopped sending drones into Israel for six years, before picking up again in 2012. On October 6, 2012, Hezbollah sent an Iranian "Ayub" drone into Israel, seemingly sending it to the town of Dimona, the site of Israel's nuclear weapons complex. After shooting down the drone, Israeli military examined the wreckage and claimed that the drone had the capability of communicating information about the nuclear facility back to Hezbollah. Weeks later, a member of the Iranian parliament claimed that the nation had received images of Israeli nuclear facilities from the drone.33
In its summer 2014 conflict with Israel, Hamas also appeared to be interested in the psychological dividend of having drones, taking to Twitter to brag about having "armed drones." Israel, for its part, was unimpressed and ultimately shot down two of the drones, which appeared to be quite rudimentary and far from the advanced drones that the United States has been using for counterterrorism.34 In the conflict with Hamas two years earlier, Israel reported that it had targeted a Hamas drone production facility. Persevering as though drones confer prestige, Hamas flew a drone in its December 2014 memorial to mark the group's 27th anniversary, prompting Israel to scramble warplanes, though the aircraft never crossed into Israeli airspace.35
Because of the potential limitations of drones in a conventional conflict the terrorist activity associated with drones is more likely to occur in a less conventional setting. For example, the type of lone wolves that carried out the hostage attack in Sydney, Australia in December 2014 or the Boston Marathon in April 2013 could find a drone well-suited to a terrorist attack, insofar as the aggressor could fly the drone remotely into a crowded area, maximizing damage, or at least maximizing psychological terror. Unfortunately, much as the non-drone terrorist strikes are difficult to guard against, those involving drones would also be quite complicated to defend against because drones are both small and also legally available for hobby and commercial uses, making the sight of a drone in an urban setting perhaps unusual but not necessarily alarming.