Ideally, access to drones would be limited to only those people and organizations that could be trusted to use them responsibly. In practice, however, attempts to limit their spread through nonproliferation efforts would face significant challenges. The core information technologies used in small drones—extremely small video cameras, chips to process video and high-speed wireless communications systems—are routinely found in inexpensive consumer electronics products. There is a large and growing set of do-it-yourself hobbyists who in some cases build remarkably sophisticated and capable drones. In addition, because drones are manufactured in many different countries and are increasingly available on the global market, efforts within any one country to limit their spread would have little global effect. And given their many legitimate nonmilitary uses in applications such as law enforcement, surveying and monitoring of infrastructure such as oil pipelines, banning their sale is impractical.
Whereas the overwhelming majority of people who build or buy drones would never consider using them for harmful ends, as the number of UAVs and people who have related expertise continues to grow, it is inevitable that they will attract the attention of terrorist groups. In fact, they already have. The Colombian insurgent group FARC, the Japanese Aum Shinrikyo sect that carried out the 1995 Tokyo subway attack, and al Qaeda have all reportedly considered the use of drones (pdf) (pdf), although there is no evidence that any of these groups employed them in an actual attack.
The security threat posed by drones has been considered before. In 2004 a U.S. House of Representatives subcommittee heard testimony regarding the threat from Dennis Gormley of the Monterey Institute of International Studies's Center for Nonproliferation Studies. An unclassified 2005 report issued by the federally-funded Institute for Defense Analyses (pdf) observed that a drone " could be fired from beyond visual range at a target while the terrorists make their escape before impact" and that there " would be little danger of detection in transportation, launch or escape."
What is new, therefore, is not the recognition that drones pose a security threat, but the changes in technology in the last few years that have greatly increased the extent of the threat and the challenges of responding to it. In the early 2000s UAVs were typically considered jointly with cruise missiles in nonproliferation discussions. But times have changed. Due in large part to information technology advances, today's drones are in some respects more similar to smart phones than to cruise missiles—both in terms of size and in terms of how easy they are to acquire.
This does not mean, however, that there is nothing that can be done. Drones could be equipped with kill switches and hidden tracking software that would enable them to be disabled or traced if they go missing. An appropriate combination of domestic regulation and international nonproliferation efforts could help reduce, although not eliminate, the possibility that drones will fall into the wrong hands. It may be possible to equip sensitive government buildings and areas with new systems to detect and, if appropriate, electromagnetically or kinetically engage low-flying incoming drones.
In the future we will no longer have the luxury of assuming that the skies above us are free of pilotless machines that might be used for to do us harm. Taking the right steps now can minimize that chance.