Editor’s note: This is the first of a two-part series on security and privacy during the age of drone warfare. Part two is available here.

The year is 2020. Two Air Force officers sit in a darkened control center at an Air Force base in Nevada, carefully watching a bank of computer screens. One of the officers gently pushes a joystick to the right, and half a world away a swarm of a dozen small drones, none weighing more than a few hundred grams, banks to the right and continues to skim almost silently across the ground at about 65 kilometers per hour toward a small settlement that has been identified as a source of possible terrorist activity. A large monitor in the front of the control center displays the live view from a night-vision camera in the lead drone. About 300 meters ahead, the first buildings pull into view.

The second officer enters a series of touch-screen commands, and three of the drones break away from the formation and begin to circle the perimeter of the settlement, acquiring video that will later be used to build a high-resolution three-dimensional model of the terrain, streets and buildings. The other nine drones fly just above the settlement, break formation and embark on a series of specialized tasks. Two drones sniff for minute quantities of chemicals associated with explosives, then combine the resulting measurements with on-site wind measurements to identify a building likely being used to store explosives. Another group of three drones with high-resolution cameras converges on the suspect building to collect imagery of the walls, roof and perimeter, including brief stops to hover outside the windows and take pictures into the interior.

The final four drones each hold a payload package slightly larger than a grain of rice containing a miniature video camera, microphone and radio transmitter. Each drone drops its surveillance payload at one of four carefully chosen sites, then retreats to a gentle landing a hundred metersoutside the settlement. There it will stay hidden in the scrub to serve as a radio repeater for the signal from the tiny bug left inside.

Science fiction? Not for long. All of the technologies to enable this scenario are either here today or close at hand. Drones, also called unmanned aircraft systems (UAS) or unmanned aerial vehicles (UAVs), benefit from many of the same technology advances that enable increasingly sophisticated smart phones, tablets and laptop computers. These advances, in combination with innovations in drone airframe and propulsion system design, are making it possible to build very small, inexpensive drones, and to control them using interfaces as simple as a touch screen, computer mouse or joystick.

Drones have transformed the way the U.S. military wages war, making it possible to gather unprecedented amounts of aerial imagery using nearly undetectable platforms, and to strike at targets without putting pilots at risk. However, these capabilities can be exploited by anyone with access to suitably equipped drones. As UAVs continue to become more numerous, smaller, cheaper and more widely distributed in the global supply chain, they will become easier to get. To believe that drones will remain the exclusive province of responsible nations is to disregard the long history of military technology. In fact, drones are already being developed and used in dozens of countries, and global spending on the technology is expected to approach $100 billion over the next 10 years.

Smaller and smaller
The amazing variety of drone shapes, sizes and capabilities reflects the diversity of the missions they are designed to carry out. Some are engineered primarily to provide surveillance, whereas others are armed. There are jet-powered drones nearly as large and fast as commercial airplanes that can be quickly deployed to locations hundreds or even thousands of kilometers away, and large blimps that can sit in the sky for months on end surveying hundreds of square kilometers at a time. But it is the small drones that have the greatest potential to impact national security and privacy, because they can be easily acquired and transported and can be almost undetectable when they fly.

Small drones are already a military operational reality. The Raven drone used by the U.S. military weighs less than two kilograms and is hand-launched by a soldier who simply throws it into the air. Once aloft, it flies to its destination and acquires both conventional color video and night vision–capable infrared video of a target. At the end of a mission it returns and automatically lands itself, after which it can be recovered and readied for its next task. During the summer of 2011, Libyan rebels conducted aerial surveillance using Scout, a 1.4 kilogram, helicopter-like drone made by Canadian company Aeryon Labs.

"Micro-drones" in the laboratory are even smaller. The prototype Nano Hummingbird developed with DARPA support by California-based AeroVironment weighs about 18 grams, has a wingspan of just over 15 centimeters, and has video capability. And Air Force researchers at an Ohio air base have built a "micro-aviary"—an indoor flight laboratory for testing drones being developed there that fly by flapping their wings in the manner of insects.

As technology continues to advance, it will become easier and less expensive to build ever-smaller drones. Small drones can help keep soldiers in the field safe, provide law enforcement officials with an important tool for monitoring crime scenes, and offer search-and-rescue teams a way to rapidly survey an area hit by a natural disaster. If they fall into the wrong hands, however, they can be used for malicious purposes as well.

Security concerns
For most of the history of warfare, getting close enough to carefully scrutinize a target has often meant incurring the risk of becoming one. Armed drones upend this axiom by bringing weaponry close to a target while simultaneously providing high-resolution, real-time video to an operator kilometers away. In the hands of a responsible military this capability is a game-changing asset; in the hands of a rogue group it is a chilling threat.

Much of the security infrastructure that exists today to limit access to sensitive locations has little effect against drones. UAVs can fly over fences and walls and can escape detection by traditional radar systems designed to track larger, passenger-bearing aircraft. Because they can be transported in the trunk of a car or in a backpack, they can be launched from any publicly accessible park, parking lot, city street, river or highway. Once airborne, a drone can arrive within minutes at any location within a few kilometers of the launch site. In short, there is no city, neighborhood or building on the planet that is beyond their reach.

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.

The future
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.