Key Insights
- UK prisons recorded 1,712 drone incidents in the year to March 2025 — a 43% jump on the prior year and more than 10× the 138 logged in 2021. That’s over four drone events every day.
- Organized groups run decoy tactics: one drone draws staff to the wrong side while a second delivers. Payloads now include phones, weapons, and fentanyl-laced paper.
- Passive acoustic detection works at night, catches autonomous drones, covers the full perimeter affordably, and is legal where jamming is not.
Drones have become the preferred tool for smuggling contraband into prisons. Small, cheap, and flown by pilots standing well outside the wall, they drop drugs, phones, and weapons into yards at night, then leave before staff can respond.
Passive acoustic detection places sensors around the perimeter to detect these drones on approach and alert control rooms in real time. It works at night, catches small and autonomous drones, and stays legal where jamming isn’t.
The scale of the problem
The numbers are rising fast. In England and Wales, UK Ministry of Justice data recorded 1,712 drone incidents at prisons in the year to March 2025 — a 43 percent increase on the previous year and more than a tenfold rise since 2021, when 138 were logged. That’s over four drone events every day across roughly 120 prisons.
The pattern repeats elsewhere. The US Federal Bureau of Prisons reported 479 drone incidents in 2024, up from 23 in 2018. Several state systems now describe near-nightly drone activity. Payloads have grown from small drug packages to phones, weapons, and fentanyl-laced paper. A single organized group in London reportedly ran around 140 flights over three months.
Governments are treating this as its own security category. The UK introduced 400-meter no-fly restriction zones around all closed prisons in January 2024, committed tens of millions to prison security including anti-drone measures, and launched an innovation competition in 2026 that explicitly draws on Ukraine’s battle-tested counter-drone technology.
Why prisons are hard to defend against drones
Prisons combine several conditions that defeat conventional detection:
- The drops happen at night. Optical and thermal cameras need line of sight, and darkness plus a narrow field of view leaves most of the approach unseen.
- The pilot stays outside the perimeter. Physical barriers, netting, and reinforced windows stop or slow a payload but detect nothing — and they don’t touch the operator who launched from a nearby street or field.
- The drones are small and increasingly autonomous. A sub-2 kg drone barely reflects radar. A drone flying a pre-set GPS route carries no radio link for RF systems to intercept.
- Jamming is off the table. Disabling or jamming a drone is restricted to specific authorities and generally illegal for a facility to do on its own. It also risks interfering with legitimate signals in a dense urban area.
- Operators use decoys. One drone draws staff to the wrong side of the site while a second delivers on the opposite side. That rewards full-perimeter coverage over a single sensor.
As one senior UK police officer put it: forces don’t police the airspace, and organized crime has learned how hard drones are to intercept.
Why acoustic detection fits prisons
Passive acoustic detection answers these conditions directly.
Sound doesn’t depend on light or line of sight. A drone approaching at 2 a.m. over a wall is as detectable as one at noon. Small, low-flying, and autonomous drones all produce motor and propeller noise — the one signature every powered drone must emit, whether or not it carries a radio link.
The sensor only listens. It transmits nothing, needs no RF license, and does not jam, so it fits a prison’s regulatory constraints. GDPR isn’t an issue — microphones capture propeller noise, not conversations, and the data isn’t personally identifiable.
At low thousands per sensor, a prison covers its full boundary and yards with a mesh of nodes rather than one costly installation. Askalon field tests reached 1 km detection on a 1 kg drone, and typical prison sites need only a handful of units. Solar or grid power and an IP67 ruggedized housing let sensors sit on walls, fences, and rooftops without wiring every position.
On detection, the sensor pushes an SMS or control-room alert, giving officers the seconds they need to respond, lock down a yard, or task a search before the payload is recovered.
Detection is the layer prisons are missing. Netting and reinforced windows are physical mitigation that acts only after a drone arrives. Acoustic detection provides the early warning and the incident record that let staff respond — and that build an intelligence picture of when and where drops happen.
What to look for in a prison drone detection system
- Passive operation, so it is legal in the sensitive zone and cannot be jammed or detected.
- Detection of small and autonomous drones, not only radio-controlled ones.
- Reliable night performance without dependence on line of sight.
- Full-perimeter coverage at a cost that scales with area, not per-unit price.
- Real-time alerting into the control room and to staff phones.
- Ruggedized, low-power hardware that mounts anywhere and runs on solar where needed.
- A data and reporting trail that supports incident review and prosecution.
Frequently Asked Questions
Can you detect drones flying over a prison at night?
Yes. Acoustic detection identifies drones by motor and propeller sound, which doesn’t depend on light or line of sight. Night approaches are as detectable as daytime ones. Cameras alone struggle in darkness.
Why can’t prisons just jam drones?
Jamming and disabling drones is restricted to designated authorities and generally illegal for a facility to carry out itself. It also risks disrupting legitimate communications nearby. Passive detection is legal and does not interfere with any signal.
How many sensors does a prison need?
Most prison sites are covered by a small mesh of sensors placed around the boundary and yards, sized after a site-specific acoustic assessment. The 1 km detection range means the count is typically in single digits for a standard facility.
Does drone detection stop the contraband?
Detection provides the early warning and location that let staff respond in time, lock down affected areas, and recover payloads. It builds the incident record needed for investigation. It works alongside physical measures like netting rather than replacing them.
Bottom Line
Drones now deliver contraband into prisons at scale — over four incidents a day across England and Wales alone. Cameras go blind at night, radar misses small drones, RF misses autonomous ones, and jamming is illegal. Passive acoustic detection covers the full perimeter day and night, catches the drones that other systems miss, and gives staff the early warning and incident data they don’t have today.
If you’re responsible for correctional facility security, get in touch — we’ll help you assess what coverage looks like for your site.
Last updated: July 2026. Reviewed by the Askalon Industries engineering team. Askalon Industries builds passive acoustic drone detection sensors in Lausanne, Switzerland.
