Improvised Explosive DevicesImprovised Explosive Devices research

Drones and the IED threat

Executive Summary

Recent years have seen a marked and rapid technological development in the capacity and availability of drones or ‘Unmanned Aerial Systems (UAS)’. And, as with so many technological advancements, it has not taken long before such drones have been employed by those who seek to spread terror.  Today, with limited financial investment and minimal innovation, terror groups can use drones to gather information or – of more concern – to modify them for use as improvised guided weapon systems.

Most notably, over the past two years, drones have been increasingly used by terror groups as the means to deliver improvised explosive devices (IEDs). And the methods used for weaponising such consumer drones have been shown to be simple and effective.

Frustratingly, the technology and systems to mitigate the risk from such attacks are still developing, and are not currently widely available or deployed routinely.  The size of the explosive device that can be deployed by a drone is comparatively small compared to most IEDs, however. Nonetheless, the ability to deploy such weapons to a specific, vulnerable location, at speed and with accuracy, is significant. The implications and responses to this threat will be examined below.

Throughout this paper the term “drones” will be used to describe all Unmanned Aerial Systems.

Historical Context

The use of drones to strike terror in populations may feel like a new concept.  But, as with many terrorist techniques, history teaches us that what we see as “new”, isn’t that new at all.

On August the 22nd, 1849, Austrian forces laying siege to the city of Venice carefully fitted explosive charges to 200 unmanned aerial systems. These balloons were released from an offshore platform, allowing the wind to carry them gracefully over the city. But each balloon was far from graceful, as each carried a bomb; a pear-shaped vessel filled with gunpowder.  The designer, the Austrian artillery officer Franz von Uchatius, was able to “programme” the balloon flight by pre-releasing smaller balloons, enabling him to calculate wind speed and direction. The bombs were to drop after 23 minutes, released by an ingenuous burning fuse mechanism.

In World War Two, similar devices were also used by both the British, who sent balloons trailing long bare wires to short circuit German power lines, and the Japanese, who sent high altitude balloons driven by the jet stream all the way across the Pacific to drop incendiaries onto North American forests.

With somewhat more proactive control systems than the use of the wind, Nazi Germany also employed radio-controlled guided bombs. These were called the “Fritz X” by the Allies, and British sailors were shocked to see high-altitude aircraft dropping bombs miles away, but then seeing the bombs track towards them in a manner quite unexpected. Later the Henschel HS-293 remotely controlled glide bomb, with a range of about 9 miles, was used to attack Allied shipping.

Figure 1 Henschel HS-293 remote controlled glide bomb. Image from – Public Domain

On a larger scale, the United States Army Air Forces (USAAF) and the United States Navy (USN) formed “Operation Aphrodite”.  This was intended to remotely pilot B17 and PB4Y bombers as precision guided munitions against hardened enemy facilities, such as U-boat pens and V weapon launch sites.  Typically, the aircraft were stripped of all unnecessary systems and loaded with a huge amount of explosives. They had a human pilot and flight engineer who “bailed out” after take-off, with the plane fitted with TV cameras and a radio control system, so it could be steered by an accompanying aircraft.

Since the end of WW2, at least until recently, the technology required for Unmanned Aerial Systems has generally been exclusive to national governments, with the budget and access to control technology that was required to effective control these weapons. But, particularly in the last four years, technology has become both available and cheap enough for the general public, including Non-State Actors (NSAs), to purchase and operate their own remote controlled airborne devices. There have been numerous attempts by NSAs to use model aircraft for attacks or reconnaissance. While the blurring of lines between nationally developed UAVs and consumer drones, has been seen in Hezbollah’s use of Iranian supplied drones to overfly Israel in the last decade.

This technological development has been matched in parallel by manufacturing companies taking UAVs to markets as “consumer” items.  It is no exaggeration to say that millions of drones will be sold in 2017.  We face a double impact of game changing technology available to anyone in the world at a relatively cheap price. Defence and Security organisations have largely been caught napping by this change.

In terms of impact, so far the harmful impact of this development has been largely felt on the battlefields of Iraq and Syria. As a US military commander in Iraq described in 2016, the step change in the threat has impacted operations:

“About five or six months ago, there was a day when the Iraqi effort nearly came to a screeching halt, where literally over 24 hours there were 70 drones in the air,” Thomas recounted. “At one point there were 12 ‘killer bees,’ if you will, right overhead and underneath our air superiority.”

Another indication of the significant change seen in the last few years is the release of videos by terrorist groups showing consumer drone use – occurring as early as May 2014. IntelCenter recorded 9 instances of videos showing terrorist use of consumer drones that year, in total. In 2015, 37 such videos were released. As of 21 November 2016, 137 such videos were released that year.

The first video of a consumer drone being used to drop an explosive device occurred in September 2016 and dozens have been released since then.  At least 15 different terrorist groups have released videos showing them using consumer drones.

Of greater concern, of course, is the fact that there is nothing intrinsically keeping drones used for nefarious intent only on the battlefield. The IED-carrying drone is now the poor man’s guided weapon, available at a cost of less than $1,000 dollars, with the added benefit of easy availability, re-usability, and with built in propaganda effect.

Why drones?

First, drones allow a terrorist to avoid and circumvent traditional security measures, or even battlefield defences, simply by flying over them.

Second, the operator can remain behind cover, out of sight of targets and enemy, to conduct the attack from a position of safety: they do not even require “line of sight” to a target, thereby lessening the risk in conducting the attack.

Third, recent advancements have enabled operators to drop IEDs from a drone with great accuracy; such attacks are therefore efficient and the accuracy outweighs the relatively small size of the IED.

Fourth, modern consumer drones are relatively quiet and very hard to spot in certain battlefield conditions, enabling the attacker to achieve tactical surprise.

Fifth, the drone operator is able to film the attack from on-board cameras, generating a propaganda of the deed to suit modern social media.

Sixth, the images transmitted to the operator can also prime other attacks, and provide surveillance of the targets.

And, finally, the drones are relatively cheap, and often reusable; compared to the price of, say, an expensive anti-tank missile, a drone that can drop cheap improvised munitions such as grenades at the price of a few hundred dollars.

So powerful are the advantages of this form of weapon that conventional military commanders have claimed that that terrorist use of drones is their most challenging problem on the battlefield. And, of course, drones are not constrained to battlefields: the potential for terrorists to deploy IED carrying drones in areas other than war zones is very real indeed.

Technological Developments

Several recent developments in technology have enabled modern drones and the opportunities they provide for terrorists. Control technology, for instance, has advanced considerably. Two decades ago, the British Army examined the utility of “remote control helicopters” as reconnaissance vehicles in support of hazardous bomb disposal operations, but the project faltered, owing to the challenges of training pilots: one required the same skills then to fly a remote-controlled helicopter as to fly a full-blown helicopter.  Modern technology today, though, has automated much of the “skill” needed to use such a system.

First Person View (FPV) technology adds to the potential ability of a controller to seek out and deploy a payload to a target, avoiding obstacles in real time.  Communications infrastructure available to the public (such as 4G) can be used and exploited by drone users to control drones and such communication networks may even have advantages over the use of more-common industrial, scientific, and medical radio (ISM) band control frequencies.

Multi-rotor technology has also advanced, with quad or octo systems providing steady, easily controlled flight. Collision avoidance technology is also now feeding through to commercially available drones, as are navigation systems such as Global Positioning System (GPS) controlled waypoints and “return to launch” capabilities.  “Default to hover” technology, which automatically makes the drone hover if hands are taken from the controls, was unheard of just a few years ago.

Battery technology can now provide significant flight duration, increasing both range and possible payload weights.

Modern drone systems also use a range of radio frequency (RF) technology that is now cheap and freely available, along with commonly available systems such as smart phones and tablets as control systems.  Internet communication has enabled the easy transfer of third party “add-on” technology to a range of commercial drones. Easily available instructions such as add on aerosol release mechanisms or IED release switches can be downloaded by anybody, anywhere in the world.

Some specialised drones have payload release mechanisms that can be also be weaponised.  Switches on drones used for cinematography or crop dusting (spraying) provide just two examples.

The speed of commercially available drones is increasing, making them faster and more difficult to interdict. In addition, swarm control systems are now coming to market allowing users to control multiple drones safely and easily at the same time.

The size of effective drones has decreased making them more difficult to detect by systems such as radar.

The cost of these systems have dropped and are globally available. The cost is now so low that the market for drones is now huge and millions are expected to be sold in coming years.

Furthermore, the legal system in most countries is struggling to “catch up” with technology to impose appropriate controls.  Issues such as drones entering commercial flight paths are among the numerous challenges that drones are presenting to governments worldwide.

Implications to the Terrorist

The implications of all of the above to the terrorist are significant. Drones can be purchased easily, anywhere, by anyone for a few hundred dollars and it will be very difficult to prevent terrorist access to this technology.   Innocuous drones can easily be adapted for terroristic purposes with little engineering skills required.

Drones can be used to insert a hazard at great speed.  Given that one of the key aspects of counter-terrorist security measures is the principle of establishing a secure perimeter, within which a search has removed any hazards, drones can circumvent that basic security measure.  The accuracy of the drone in terms of piloting means that targets not previously considered vulnerable even to significant terrorist weaponry are now vulnerable. A drone can approach a critical component or a key person, at high speed, and can even enter a building in some circumstances. The piloting skills required are minimal, and the range of the system can place the pilot easily outside secured areas.

Payloads are still relatively small, but given the ability to place a hazard at very close proximity to a target, this is perhaps less of an issue. Swarms can overwhelm a number of counter measures.  A drone also offers a terrorist a cheap and effective reconnaissance and propaganda tool.

Examples of Terrorist use or similar indicative use of drones

In many ways, the issue posed by drones is already extant. Non-State Actors are widely using drones today, in Syria and Iraq, for reconnaissance and propaganda, and for dropping IEDs accurately on to targets.  Such operations are allowing terrorists, of all varieties, to rapidly develop tactics and technology to optimise attacks.  The genie is out of the bottle.   Indeed, the then British Prime Minister David Cameron warned that terrorists have already tried to obtain crop spraying drones for the purpose of spreading radiological material.

The success of the terror drone is also very evident. Social media has transmitted hundreds of images of drones dropping small grenade-like IEDs on targets in Syria and Iraq. Indeed, even Iraqi security forces, facing Daesh, have adopted this technology for their own ends.

Figure 2. Syrian rebel drone propaganda footage of an explosion in Aleppo. Note too the artillery projectile that by chance was by chance caught by the drone camera. Screen shot from Al Nusra released video at

Figure 3. Screen capture from Amaq News showing a Daesh improvised grenade dropping on a vehicle from a drone. The drone subsequently hit the targeted vehicle and caused the ammunition it was carrying to detonate, destroying the vehicle.

Likely threat evolutions

The threat from drone-delivered IEDs will continue to evolve, and the operating environment in Syria and Iraq will allow users to learn rapidly new lessons and to test new methods of attack.  There are, in this way, a number of methods by which this threat will likely continue to provide new challenges.

First, IED payloads are likely to increase in size, as a result of larger drones or more powerful motors. This will make the drones yet more attractive to the user for delivering larger payloads.

Second, the relatively crude methods currently used to counter drones will push developers to harden their vulnerability. Currently many drones are vulnerable to electronic counter-measures (“jamming”) and it is likely that a traditional technology versus technology battle will drive the threat in new directions.

Third, swarms of drones are expected to be increasingly used, overwhelming traditional counter-measures. It is also very likely that the IED carrying drones will appear in areas outside of the current theaters of war in Iraq and Syria.  Daesh, for example, have shown a propensity to take its attacks to Europe and attack high profile population dense targets in order to gain the press attention they seek so dearly.  The additional value to the propaganda of the deed, by ensuring the drone films their attacks is also significant to the terrorist.  It is also possible that the capabilities of a drone-delivered IED will enable terrorists to attack targets which hitherto have been beyond their current capabilities.

Implications to Security Measures

Security measures are impacted by the evolving capabilities of drones in a number of ways. There is a need to think somewhat differently about security.  While many targets – both military and humanitarian – were once vulnerable to terrorist mortars or rockets, the potential accuracy of a drone-delivered hazard to any location demands a rethink.  Drones can enter buildings through open doors or windows, manoeuvre, and can be placed within inches of a vulnerable target, controlled from great range.

Drones can be relatively stealthy. The drone that landed two years ago on the Japanese Prime minister’s roof carrying a payload of alleged radio-active material was discovered only by chance some days later. Other drones have “crashed” on prison roofs delivering contraband and not been discovered for some time.

As well as providing complex threats, drones also provide a simple hazard if control is lost and they fall on those people underneath them – security measures need to bear that in mind – causing a drone (even without a payload) to crash can kill people. And the wide availability of drones will mean even the foolish may have the opportunity to fly what has been described as “an airborne lawn mower” over crowds of people at concerts and other major events. As such, mitigation systems that offer the ability to take control and land drones are preferable over those that simply cause drones to fall from the sky.

Secure perimeters surrounding a cleared area, may not remain so. A drone can deploy a hazard to the area after it is secured.

Technology continues to advance rapidly – the threat posed by drones is and will remain highly dynamic in nature.  The ingenuity of third party drone adaptations will reinforce that.

The legality of establishing certain drone counter-measures has yet to be tested. Drones pose other security threats beyond terrorism; protection from cyber threats – such as a drone flying a wi-fi access point into a secure area, or filming sensitive activities or filming sports events for which TV rights belong elsewhere – all pose challenges.

The presence of a drone will not always equate to a threat.  Drone use for legitimate purposes is likely to mushroom in coming years; such that there may well be many legitimate drones in the air near a secured facility.  Separating threat drones from legitimate drones will be a challenge.

Drone threat response plans need to be flexible and integrated both with other security measures and with any counter-drone solution. Some current or developing counter-drone solutions are not holistic and only answer part of the question.

Security measures will need to be compliant with local regulations and legal structures. Some measures will need appropriate authorisation which will need to be balanced with the potential of a drone threat being detected say at 250m, and then being immediately adjacent to a vulnerable target just seconds later, 24/7.  Drones pose challenges to the speed of security responses and will require immediate decision making: a reality that might run counter to some concerns about fully automated responsive weapon systems.  There may be little time for formal, slow time authorisations and so pre-authorisation of certain security measures – and the implications of such – may be an issue for the near future.

The drone threat can be highly dynamic.  If a drone – or a swarm of drones – lands in a facility adjacent to vulnerable component “X”, a security plan might be implemented, an evacuated cordon put in place and a command post established. Then the drone, within seconds, relocates to vulnerable point “Y”, or even to an evacuation point elsewhere in the facility. Theoretically, a drone can chase crowds evacuating from a building, thereby causing significant panic. Most hazards detected in a secure facility will remain stationary and most security plans assume that. However, a drone might not; this would demand, accordingly, far more agile security plans. A key requirement of counter-drone systems, then, could be to maintain the mitigation effect until such time as the threat is otherwise immobilised.

Any terror-threat drone captured or shot down will hold significant forensic intelligence value and security plans should recognise that.

It may be difficult to establish the nature of any hazard from payloads. In essence, they should be treated like a Radio Controlled IED until such time as the proper authorities have mounted their response.

Swarms of drones also need to be considered. Technology to control swarms of drones is already available and counter-drone systems need to be capable of responding to a number of drones at the same time.

In some circumstances, a counter-drone system can provide an effective deterrent measure.  In this sense, the drone threat and counter-measure situation is unusual. There is no counter-measure that can prevent a shooting completely or a rocket or mortar attack. But the more effective counter-drone systems can mitigate certain drone attacks completely.

Drone Counter-measures
Just as the market for drones is increasing, so too is the market for drone counter measures.  It is not the purpose of this article to recommend one or other of the available or soon-to-be-available counter measures. But the following may be considerations:

  1. There will be one or more elements to a counter-drone system, that might include:
    1. Detection
    2. Alarm
    3. Identification
    4. Categorising as a threat
    5. Tracking
    6. Mitigating/Active measures
      For counter-drone systems that do not offer all of the above, then consideration needs to be addressed to the others in a coherent plan.
  1. Depending on the nature of the secured area or potential target for threat drones, there may or may not be a need for a 24/7 capability, and by implication, operations in the dark.
  2. Some systems may be automated, some will require man-in-the-loop.
  3. Some measures may require appropriate authorisation. “Jammers” may not be legal in certain jurisdictions.
  4. “Jammers” which cause a drone to land or crash wherever it is at that moment in time may complicate matters further and could pose a threat to civilians. In those circumstances, more advanced systems that take control of the threat drone and enable it to be landed in a pre-designated safe zone may have attractions.
  5. Some counter-measures can deal with “swarms” of threat drones others cannot.
  6. Some require line of sight, others do not.
  7. Some can operate at night, others cannot.
  8. Some require minutes or more to deploy an active counter measure, others can do it at speed. Rapid response to the drone threat brings with it its own legal complexities.


Roger Davies MBE QGM, for AOAV.