Image: GPSJam.org & RNT Foundation

What’s new: Persistent GPS interference detected in and around Sofia, the capital of Bulgaria beginning on 12 December 2025.

Why it’s important: PNT signals from GPS underpin all kinds of critical infrastructure and applications. Interference has the potential to cascade through a society and economy.

What else to know: This interference may be coincidental, or part of efforts by Russia or others to destabilize Bulgaria. 

• On the 12th of December, the day the interference started, the EU decided to include Bulgaria and Romania in the Schengen visa-free zone, effective January 1, 2025. Vladimir Putin has a history of using GPS jamming and spoofing to show his displeasure with neighbors growing closer to the west.
  • In 2022, after he warned Finland against trying to joint NATO, the Finnish president met with U.S. president Biden. Russia jammed Finnish air traffic immediately thereafter.
  • On the 15th of December 2023 Poland activated a U.S. Aegis anti-missile system near its border with Kaliningrad, Russia. The same day Russia began jamming and spoofing GPS signals in northern Poland and parts of the Baltic. That interference persists to this day.
• Bulgarian politicians have been struggling to form a new government since elections in October. The 10th of December saw the beginning of a new attempt. Interference with GPS can undermine overall confidence in government systems and institutions and contribute to instability – another of Putin’s goals for unruly neighbors.
• 20,000 households in western Bulgaria (Sofia is in the far west) have been without electrical power since Christmas. Press reports put this down to heavy snow and fallen trees. Many grid operators use GPS timing to help manage their systems. We wonder if this might also be a factor.
• The interference seems to be coming from somewhere in Sofia, not from Russian territory as is the case in the Baltic. If this is a Russian punishment/ destabilization effort, it is an internal Bulgarian security problem.
• The interference was detected through the aviation safety ADS-B system which uses GPS. We have no information as to if Europe’s Galileo satnav system is also being impacted. GPS and Galileo operate in similar frequency bands so disrupting both at the same time is fairly easy.

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