Defeating drones: beyond the headlines


Energy beams. Cannons that shoot nets. Trained falcons. There are dozens of headline-grabbing solutions to threats posed by the hostile or careless use of drones. But the most newsworthy countermeasures are not always the most effective.

Obsidian Counterdrone Graphic depicting a drone or UAV flying outside of an exclusion zone dome in a 3D cityscape

The use of commercial off-the-shelf drones for nefarious purposes – whether espionage, smuggling, disrupting essential services, damaging property, or harming people – is a problem widely acknowledged but often poorly understood. Faced with this relatively new emerging threat, at-risk organisations are still in the early stages of assessing their vulnerabilities and considering their countermeasures. Media hype has already led to instances of customers panic-buying some of the better-publicised solutions, only to discover unforeseen barriers to the equipment’s use that render it largely ineffective. 

To be clear: the ability to neutralise a drone quickly and safely is a vital part of the defensive arsenal. One can imagine any number of scenarios in which decisively incapacitating a hostile drone could be lifesaving, such as protecting a nuclear reactor or a packed sports stadium from improvised airborne explosives. Many of the emerging technologies designed to defend against these threats are very proficient at it. However, most of them have inherent limitations, or produce unwelcome side-effects that would make any organisation think twice before deploying them. That hesitation could prove fatal. 


Effectors and side-effects

An effector (a device used to incapacitate a drone) can usually be placed into one of two categories: kinetic, or radio frequency (RF). Kinetic effectors, such as net launchers, are generally limited by the requirement that they be activated within close proximity of their target. Looking back to the drone sightings that grounded air traffic at Gatwick Airport over three days in December 2018, it was not possible even to locate the reported drone, let alone get close enough to capture it.  

RF effectors employ different parts of the electromagnetic spectrum, ranging from low-energy jammers that intercept the drone’s navigation system or the communications link with its pilot, to high-power directed energy that disrupts the aircraft’s circuits or motor control signals. These can hypothetically be deployed at longer range, but are limited by a lack of evidence around their potential for unintended collateral effects. Deploying an RF jammer to bring down a drone could do more harm than good if, for instance, it takes down the organisation’s own communications with it. The user must also consider what else in the vicinity may be affected, and the third-party liabilities that may result. For example, what would be the costs and consequences of inadvertently disrupting the servers of a nearby bank or business? Until these factors are better understood, regulations will remain in place to restrict the use of RF countermeasures in populated areas.  

None of this is to say these countermeasures should never be deployed – just that doing so should usually be an organisation’s last resort, not its first. Given the potential for negative side-effects, these should be weighed up against the severity of the threat and a quick decision made as to what type of action is proportionate. Effectors should therefore form part of a layered strategy, in which their deployment is the final step of escalation. In the counter-drone iceberg, effectors are just the tip. 


The bulk of the iceberg

If an effector is the top level of escalation, we need to consider the other levels that precede it. Starting at the very bottom, if a drone poses no threat then taking no action is an option. The drone may be flying with a permit and simply going about its business with no hostile intent – in which case, shooting it down could result in a very angry owner. 

Moving up the scale, there may be occasional low-level cause for concern, such as a drone flying within line of sight of a meeting room in which a confidential presentation is being given. It may sound glib, but if it is an isolated case the most effective course of action might be to close the blinds rather than invest time and resources in locating and removing the drone. 

For recurring suspicious incidents that do not pose an urgent threat, a longer-term strategy of monitoring and analysing patterns of occurrences may be most appropriate. Gathering evidence about the times and locations of incidents could enable security teams to apprehend the drone’s operator, allowing questioning and prosecution if necessary to prevent further offences. 

Moving up a level, if a moderate threat is suspected a deterrent may be the next step. For example, deploying a highly visible security patrol around the site’s perimeter may lead the drone operator to conclude the activity is too risky, forcing them to pack up and leave the area.

All of these options precede the deployment of effectors in the escalation of response. The examples are purely illustrative, as the specific needs of each organisation are likely to be unique, but they demonstrate the type of layered strategy a security team can put in place to ensure a proportionate response to any type of suspicious drone activity. 


Proportionality of response

A counter-drone strategy can be considered successful if the response is consistently proportionate to the threat. This means not overreacting in ways that cause unnecessary disruption, or underreacting in ways that expose the organisation to risk. This can only be achieved if the nature and severity of threats are fully understood.

The 2018 grounding of Gatwick flights in response to reported drone sightings is estimated to have cost airlines up to $64.5m. That figure is negligible compared to the human cost of losing an aircraft, so could be considered entirely proportionate if a drone attack was indeed underway. However, if the reported sightings were hoaxes or misperceptions, and there were in fact no drones, the response and resulting losses could be considered wildly disproportionate. The problem at Gatwick was that the truth was unknown, so the only available option was to assume the worst and react accordingly. Whether or not this was an overreaction could not be known at the time and cannot be fully established even now.


Situational awareness

What would it take to confidently refute a bogus drone sighting? And how can an organisation be sure that its response is proportionate to any given threat? Both of these demand wide-ranging and persistent awareness of the surrounding air environment, coupled with the ability to quickly identify threats and classify their severity.

To be confident that a drone is not present requires a large body of evidence that gives a comprehensive oversight of the local airspace and everything in it.  A number of technologies are available to achieve this, including RF sensors (measuring the direction of drone/pilot) signals, radar, video and acoustics.  These have their relative merits, however our analysis has shown that radar is the most resilient and threat-agnostic technology for detection and tracking of drone threats.  Furthermore, as not all radar are equal, chief among radar systems are 3D radars, capable of measuring not just range and bearing to the drone, but also its height, providing true location in 3D space.
Such a 3D radar system can precisely locate and track drones, allowing accurate and automated set on of camera systems for visual threat identification – but crucially it can also be used over time, in the absence of drones, to establish what the normal pattern of daily activity looks like. In the event of a hoax report, instead of waiting until sufficient time has passed with no sightings, the drone’s presence can be ruled out in a shorter timescale by comparing current airspace activity to the established baseline.

Classifying a threat must be achievable in a very short space of time, as undue hesitation could result in security breaches, damage to property, or even loss of life. Using a 3D radar as described above, the system would flag to its operator any deviation from the established normal picture. Classification may involve evidence gathered from multiple sources, including 3D radar, acoustic sensors (microphones), optical sensors (cameras), radio frequency detection, and even the naked eye. This information can be integrated to provide an instant picture of the nature of an airborne object, its location and its likely intent; based on its appearance, sound, movements, and the signals it emits.     
Finally, it’s highly likely that when legislation is passed to allow drone denial effectors to be used, they will need to comply with strict rules of engagement including precise targeting.  A 3D radar provides accurate drone location and uniquely allows the precise set-on of effectors to minimise unwanted side effects or collateral damage.  


Beyond the headlines

It won’t make national news, but the key to protecting against drones is situational awareness. A confident, proportionate response is made possible by: the knowledge of what local airspace normally looks like, and; the ability to quickly locate, identify and classify any approaching object that deviates from that normality.    

Decisions to shut down operations or deploy effectors in response to drone sightings should not be taken lightly. Comprehensive situational awareness is the decision-making engine that powers an organisation’s counter-drone capability. It enables responses to be tailored to the circumstances, preventing under- or overreactions that could cost money or lives.

The challenges of deploying RF effectors in populated areas remain. These will be addressed over time through regulation informed by testing and evaluation to observe the extent of the technologies’ collateral effects. Situational awareness may also have a role to play, by providing organisations with evidence about their local digital environments and the nearby systems likely to suffer collateral effects from any use of directed RF technology. This could inform risk assessments to further aid proportionality. However, in the meantime, knowing when not to take action may be just as critical.