UPSC Prelims 2026Question 47Security

Which of the following statements with regard to drone swarms is/are correct ?
1. They use Terahertz band of frequency to communicate with the command centre.
2. Individual drones in the swarm can communicate with other drones in the swarm.
3. GPS Spoofing is a commonly used technique to counter drone swarm attack.
Select the answer using the code given below:

Options

(a)1 only
(b)2 and 3 only
(c)1 and 2 only
(d)1, 2 and 3

Correct answer: b

Decision rule

An emerging research band is not an operational standard; a statement making a laboratory frontier the routine working technology is false.

Explanation

Correct Answer

(b) 2 and 3 only

Explanation of the Correct Answer

Statement 1: They use Terahertz band of frequency to communicate with the command centre.

Incorrect.

Drone swarms generally use radio frequency communication links, Wi-Fi-like links, mesh networks, cellular networks, satellite links, or other tactical communication systems.
The Terahertz band is an emerging area of communication research, but it is not the standard or defining communication band used by drone swarms.
Terahertz waves also face practical limitations such as atmospheric absorption and short-range propagation issues.

Hence, statement 1 is incorrect.

Statement 2: Individual drones in the swarm can communicate with other drones in the swarm.

Correct.

A major feature of a drone swarm is coordination among multiple drones.
Individual drones may communicate with:
- the command centre,
- other drones in the swarm,
- local nodes or relay drones.
This drone-to-drone communication allows the swarm to coordinate movement, share sensor data, avoid collisions and perform collective tasks.

Hence, statement 2 is correct.

Statement 3: GPS Spoofing is a commonly used technique to counter drone swarm attack.

Correct.

GPS spoofing involves sending false GPS signals to mislead drones about their actual location.
It can be used to disrupt or divert drones that depend heavily on GPS navigation.
Other counter-drone methods include:
- radio-frequency jamming,
- GPS jamming,
- directed-energy weapons,
- net-based interception,
- cyber takeover,
- radar and electro-optical tracking.

Hence, statement 3 is correct.

Therefore, statements 2 and 3 only are correct.

Why Other Options Are Incorrect

Option	Verdict	Explanation
(a) 1 only	Incorrect	Statement 1 is incorrect because drone swarms do not characteristically use the Terahertz band to communicate with command centres.
(b) 2 and 3 only	Correct	Drone swarms involve drone-to-drone communication, and GPS spoofing can be used as a counter-drone technique.
(c) 1 and 2 only	Incorrect	Statement 2 is correct, but statement 1 is incorrect.
(d) 1, 2 and 3	Incorrect	Statement 1 is incorrect.

Relevant Supplementary Information

Drone Swarms: Key Features

Feature	Explanation
Meaning	A group of drones operating in a coordinated manner
Core capability	Collective operation through communication and coordination
Communication type	Drone-to-drone and drone-to-command-centre communication
Control model	Can be centralised, decentralised or hybrid
Navigation	GPS, inertial navigation, visual navigation, terrain matching or sensor fusion
Major advantage	Can overwhelm conventional defence systems through numbers and coordination
Major risk	Can be used for surveillance, electronic warfare or coordinated attacks
Common countermeasures	Jamming, spoofing, directed energy, nets, cyber takeover, kinetic interception

Communication in Drone Swarms

Communication Mode	Meaning	Use in Swarms
Drone-to-drone communication	Drones exchange information among themselves	Enables coordination, formation control and collision avoidance
Drone-to-command communication	Drones communicate with a ground station or controller	Allows mission control and monitoring
Mesh network	Each drone can act as a node and relay information	Useful when direct communication with command centre is limited
Satellite link	Communication through satellite systems	Useful for long-range operations
Cellular network	Uses 4G/5G-like communication	Useful in civilian or urban environments
Terahertz communication	Very high-frequency experimental communication range	Not a standard defining feature of drone swarms

Communication Mode	Meaning	Importance
Drone-to-drone communication	Drones communicate with each other	Enables coordination, collision avoidance and formation flying
Drone-to-command communication	Drones communicate with a ground control station or command centre	Enables mission control and monitoring
Mesh networking	Each drone acts as a node and can relay signals	Useful when direct contact with command centre is weak
Radio frequency link	Wireless communication using radio waves	Commonly used in drone operations
Cellular communication	Use of 4G/5G-like networks	Useful for urban or civilian drone operations
Satellite communication	Communication through satellites	Useful for long-range or remote missions
Terahertz communication	Very high-frequency emerging communication technology	Not commonly used as the defining communication method of drone swarms

Counter-Drone Techniques

Technique	How It Works	Limitation
GPS spoofing	Sends false GPS signals to mislead drone navigation	Less effective against drones using inertial or visual navigation backup
GPS jamming	Blocks GPS signals	May affect friendly systems too
RF jamming	Disrupts control or communication links	Autonomous drones may continue mission
Cyber takeover	Exploits software or communication vulnerabilities	Requires access to vulnerability
Directed-energy weapon	Uses laser or microwave energy to disable drones	Weather and line-of-sight limitations
Kinetic interception	Shoots down drones using missiles, guns or projectiles	Costly against large low-cost swarms
Net capture	Physically traps drone using nets	Limited range and scale
Radar and EO/IR tracking	Detects and tracks drones	Small drones can be difficult to detect

Key Takeaways from the Tables

Point	Explanation
Drone swarm = coordinated group of drones	The defining feature is collective operation, not merely many drones flying together.
Drone-to-drone communication is important	It allows coordination, data-sharing and formation control.
Terahertz is not the standard communication band	It is more of an emerging research area, not the usual communication method for drone swarms.
GPS spoofing is a countermeasure	It can mislead GPS-dependent drones.
Counter-swarm defence is difficult	Swarms can overwhelm traditional defences through numbers, autonomy and distributed coordination.
Redundancy matters	Advanced drones may use multiple navigation systems, reducing the effectiveness of GPS-only countermeasures.

Point	Explanation
Drone swarm = coordinated drones	The defining feature is collective behaviour, not merely the number of drones.
Drone-to-drone communication is central	It enables coordination, formation control and data sharing.
Terahertz band is not standard	It is not the usual communication method for drone swarms.
GPS spoofing is a countermeasure	It misleads drones by providing false location data.
Counter-swarm defence needs multiple tools	Jamming, spoofing, directed energy, cyber methods and sensor fusion may all be used.
Autonomy makes swarms harder to defeat	Drones may continue the mission even if command links are disrupted.

Context and Current Relevance

Drone swarms are becoming important in modern warfare, border security, disaster response, mapping and surveillance.
Their military relevance has increased because low-cost drones can overwhelm expensive conventional defence systems.
Counter-drone technology is now focused on jamming, spoofing, directed-energy systems, sensor fusion and AI-based detection.

Table: Drone Swarms — Key Features

Feature	Explanation
Meaning	A group of drones operating together in a coordinated manner
Core principle	Collective behaviour through communication, sensing and coordination
Control model	Centralised, decentralised or hybrid
Communication	Drone-to-drone and drone-to-command-centre communication
Common communication systems	Radio frequency links, mesh networks, Wi-Fi-like links, cellular networks, satellite links
Navigation methods	GPS, inertial navigation, visual navigation, terrain matching, sensor fusion
Main advantage	Can perform coordinated missions and overwhelm conventional defences
Main vulnerability	Communication links, GPS dependence, software vulnerabilities and battery limits
Main exam trap	Terahertz communication is not the standard defining feature of drone swarms

Table: Counter-Drone and Counter-Swarm Techniques

Technique	How It Works	Important Limitation
GPS spoofing	Sends false GPS signals to mislead drones about their location	Less effective if drones use inertial or visual navigation backup
GPS jamming	Blocks GPS signals	Can affect friendly navigation systems too
RF jamming	Disrupts command, control or communication links	Autonomous drones may continue their mission
Cyber takeover	Attempts to exploit software or communication vulnerabilities	Requires access to weaknesses in the drone system
Directed-energy weapons	Uses lasers or high-power microwaves to disable drones	Weather, power and line-of-sight constraints
Kinetic interception	Physically destroys drones using guns, missiles or projectiles	Costly against large numbers of cheap drones
Net capture	Captures drones using nets	Limited range and scale
Radar detection	Detects drone movement through radar signatures	Small drones can have low detectability
EO/IR tracking	Uses electro-optical or infrared sensors	Weather, range and line-of-sight limitations
Sensor fusion	Combines radar, RF, acoustic and optical data	Requires advanced integration and processing

Table: Drone Swarms vs Ordinary Drone Operations

Basis	Drone Swarm	Ordinary Drone Operation
Number of drones	Multiple drones working together	Usually one or a few drones
Coordination	High level of coordination	Limited or manual coordination
Communication	Drone-to-drone and drone-to-command links	Mostly drone-to-controller link
Autonomy	Higher autonomy possible	Often directly controlled by operator
Mission type	Surveillance, search, attack, mapping, electronic warfare	Photography, surveillance, delivery, inspection
Resilience	Can continue even if some drones fail	Failure of one drone may end the mission
Threat potential	Can overwhelm defence systems	Easier to detect and neutralise individually
Complexity	High	Comparatively low

Table: Similar Prelims-Trap Facts on Drone Swarms

Statement / Theme	Correct Understanding	Common Trap
Drone swarms communicate internally	Correct	Assuming only command centre controls all drones individually
Terahertz band is standard for drone swarms	Incorrect	Terahertz is an emerging research area, not the common defining band
GPS spoofing counters drones	Correct	Assuming only physical destruction can counter drones
GPS jamming and spoofing are same	Incorrect	Jamming blocks signals; spoofing sends false signals
Autonomous drones are hard to stop by RF jamming	Correct	Assuming loss of control signal always stops the drone
Drone swarm means many drones flying randomly	Incorrect	A swarm involves coordination and collective behaviour
Mesh network helps swarms	Correct	Drones can relay information through each other
Counter-swarm defence is easy	Incorrect	Large numbers, low cost and autonomy make defence difficult
Sensor fusion helps detection	Correct	Combining multiple sensors improves tracking and identification

Table: Defence and Civilian Uses of Drone Swarms

Area	Possible Use
Military operations	Surveillance, decoy missions, coordinated attacks, electronic warfare
Border security	Monitoring difficult terrain and infiltration routes
Disaster management	Search and rescue, damage assessment, supply delivery
Agriculture	Crop monitoring, spraying and field mapping
Urban management	Traffic monitoring, infrastructure inspection
Environmental monitoring	Forest surveillance, wildlife tracking, pollution mapping
Communication support	Temporary aerial communication networks
Mapping and surveying	Rapid mapping of large or inaccessible areas

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