Deciphering the coordinated GPS-spoofing incidents that disrupted Indian airports
Source: Dev.to
Incident Overview
In December of last year, pilots approaching several major Indian airports reported that their navigation systems displayed valid GPS signals but with incorrect positions. The affected airports included Delhi, Mumbai, Bengaluru, Hyderabad, and Kolkata. At Delhi’s Indira Gandhi International Airport, the anomaly was concentrated near Runway 10/28, which had recently been upgraded to CAT III capability for low‑visibility operations.
GPS Spoofing vs. Jamming
- GPS jamming: Signals disappear, receivers lose lock, and pilots are immediately aware of a problem.
- GPS spoofing:
- Signals appear legitimate and correctly timed.
- Receivers continue operating normally, but with false position data.
- Automation may not disengage, and warnings may not trigger promptly.
Impact on CAT III Instrument Landing Systems (ILS)
CAT III ILS enables aircraft to land with almost no external visual reference, relying heavily on instruments during foggy conditions. ILS provides:
- Localizer – horizontal guidance
- Glide slope – vertical guidance
When GNSS (GPS) data is degraded, crews normally cross‑check with ILS. If both GNSS and ILS are compromised, redundancy collapses at the most critical moment—during the approach.
ILS Vulnerabilities
ILS is a radio‑based system without cryptographic authentication. Controlled tests have demonstrated several interference techniques:
- Overshadowing – a stronger fake signal replaces the genuine one.
- Single‑tone interference – corrupts lateral or vertical deviation calculations.
- Adaptive offsetting – slowly nudges guidance off course without abrupt alarms.
These methods are well understood in RF research circles and are not “script‑kiddie” techniques.
Combined Spoofing Scenarios
When GPS and ILS are spoofed simultaneously:
- Cross‑checks fail.
- Automation trusts corrupted inputs.
- False alerts may overwhelm genuine warnings.
- Situational awareness degrades rapidly.
In low‑visibility conditions, this combination raises the risk of Controlled Flight Into Terrain (CFIT) because systems fail quietly rather than loudly.
Implications for Air Traffic Control (ATC) and Operations
- ADS‑B and radar fusion rely on accurate position data; spoofed data creates uncertainty.
- Traffic flow degrades quickly due to go‑arounds and diversions.
- Fuel margins shrink, especially during weather disruptions.
- Multi‑airport impact compounds chaos exponentially.
Navigation trust is a shared dependency across the entire airspace.
Potential Threat Actors
Given the coordination and technical depth, likely actors are limited to:
- State‑linked threat groups testing infrastructure resilience.
- Proxy groups using commercially available spoofing equipment.
- Actors conducting dry runs rather than seeking immediate destruction.
The lack of public claims suggests the motive was capability assessment rather than attention‑seeking.
Future Outlook
Aviation increasingly assumes that navigation data is honest by default. This assumption is no longer safe. GNSS, ILS, and ADS‑B were designed for reliability, not adversarial environments. As automation grows, the cost of silent manipulation rises.
The key question is not if spoofing will happen again, but whether systems will detect it before humans are forced to react at the edge of safety margins.
Call to Action
For professionals working in:
- RF engineering
- Avionics software
- Safety‑critical systems
- Cyber‑physical security
What do you consider the weakest link today—signal integrity, system fusion, or human‑machine trust? Share your thoughts and let’s discuss.