Finnish government agency warns of unusual GPS interference from aircraft

Airplane GPS

Finland’s Transport and Communications Agency, Traficom, has made a public announcement about an unusual spike in GPS interference near the country’s eastern border.

The origin of the interference remains unknown, but based on numerous reports submitted to the agency from various sources, it started over the weekend and is still ongoing.

This has resulted in the issuing of NOTAMs (messages to pilots) to raise awareness among pilots and help them take additional measures to keep flights safe.

Notably on Sunday, several Transaviabaltika aircraft flying to Savonlinna, Finland, were forced to return to Tallinn, Estonia, due to a malfunction of the onboard GPS navigation system.

SMS notification for flight cancellationSMS notification for flight cancellation (YLE)

Traficom’s director, Jari Pöntinen, noted the following:

Flying is still safe. Airlines have procedures that they follow if the GPS signal is lost. Aircraft may use other systems to navigate and land safely. Air traffic control supports aircraft pilots using other landing systems.

As the agency’s announcement concludes, the source of the interference from the ground is difficult to determine because the inserted signals are aimed at the sky and their effects are so transient and localized that any verification is practically impossible.

GPS spoofing

GPS (Global Positioning System) is a radio navigation system that relies on a connection of four or more satellites to send geolocation and time information to the receiver.

If something interrupts that link or hijacks the receiver’s focus to a system on the ground disguised as a GPS satellite, navigation becomes unreliable.

This spoofing is relatively easy because the actual GPS signal is weak and the receiver antennas are not sensitive.

The equipment needed to carry out these spoofing attacks costs several hundred dollars, while the software to simulate realistic GPS satellite radio signals is widely available.

For example, a 1 kW portable jammer can block a GPS receiver as far as 50 miles, so there aren’t many practical challenges in launching these attacks.

What could be the cause?

GPS spoofing has been used in high-stakes targeted attacks such as yacht hijacking, but it is generally a tactic followed by the military.

There have been previous reports of navigation problems from several ships in the Black Sea, linking Russia to the 2017 incident.

In December 2017, Norwegian authorities accused Russia of widely disrupting GPS navigation during military exercises. In November 2018, NATO military exercises in Finland faced similar issues.

This time, the interference coincided with the meeting between US President Joe Biden and Finnish President Sauli Ninisto. At the moment, the country is considering joining NATO, which is not received with enthusiasm in the Kremlin.

According to reports, the interference is not limited to Finland, but also affects Poland, Lithuania, Latvia and the wider Baltic region.

I thought creating maps from GPS/GNSS interference could be boring. But 3 days ago, the Baltic Sea (Poland, Lithuania, Latvia, Kaliningrad) suddenly got some of the most significant interference on the planet, after weeks of nothing out of the ordinary. Why now?

— John Wiseman (@lemonodor) March 7, 2022

At the moment, no official attribution has been made by any of the affected countries, while the Finnish authorities have stated that they are still investigating the ongoing problem.

Can this security issue be resolved?

GPS spoofing is difficult to stop because the signal the satellites are broadcasting from low Earth orbit to potentially add encryption and certificates cannot be changed.

The only way to tackle this on the ground is to include GPS firewalls on the receivers and implement multi-array antennas to introduce a directional verification factor to the signal.

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