GPS Spoofing

The Global Positioning System (or GPS) is a satellite navigation system that uses satellites to provide autonomous geo-spatial positioning.

This technology is everywhere – it’s in your car, your smartphone, your watch, your fitness tracker, handheld GPS receivers, and more.

A handheld GPS receiver
A typical Handheld Global Positioning System (GPS) Device

But did you know that these satellite signals can be jammed – or even worse – deceived using something called GPS spoofing?

Let’s take a look at this interesting topic of discussion.

What we’re going to review here applies to any of the popular satnav systems – that includes GPS (the US satnav), Galileo GNSS (or Galileo Global Navigation Satellite System – the European version), and Russia’s GLONASS system.

How does GPS work?

There are multiple GPS satellites in orbit around the earth.

Artist's conception of GPS Block II-F satellite in Earth orbit.
Artist’s conception of GPS Block II-F satellite in Earth orbit.

Special chips can be included in nearly any electronic device that can read signals transmitted from the satellites.

And combined with a bit of math – the device can determine your position with great accuracy as long as it can receive signals from at least 4 of the satellites overhead.

Sound expensive? Yep – it is. (At least the satellite part is.)

Delta IV GPS III launch
The US GPS system is fully functional – but even still the US government is further upgrading the system to the new GPS III version – with many rocket launches to loft new satellites into orbit. (U.S. Air Force photo by Airman 1st Class Dalton Williams)

The GPS system was originally created for use by the US military – and in fact it was funded by the US government and is run by the US Air Force.

However, given that this system is so fantastically useful – the signals are available for free to anyone with a GPS receiver.

The European Union and Russia have their own versions as well, called GNSS and GLONASS respectively.

Those entities don’t want to rely on something provided by the US – for good reasons.

But, those systems aren’t as complete or robust as the US GPS system.

As such, we’ll focus the remainder of our discussion on the US based GPS system exclusively.

GPS Jamming

GPS works in a “one way” fashion.

Any device can read the signals sent by the satellites – and the device doesn’t need to “talk back” to the satellite.

That would be a daunting challenge – the satellites are very far away.

But also because of this the GPS signal that arrives at earth is quite weak.

It is also easily blocked by buildings or mountains.

Most people who have used their smartphone for nav in a big city with tall skyscrapers have experienced this first hand.

It’s also possible to jam this relatively weak GPS signal.

An earth-bound transmitter can blast out a wrong or incorrect GPS signal with ease – or flood the airwaves such that the GPS receiver can’t function properly.

It can be very close to the receiver – so it’s easy to over-power the signal coming from those far away satellites.

And so, that is the basics of GPS jamming.

Why would someone want to jam a GPS signal?

The answer is simple – to deny someone else the ability to navigate accurately and conveniently.

Remember that GPS was invented for military use.

GPS signals are used to guide bombs, missiles, and even drone weapons.

General Atomics MQ-1C Gray Eagle
The “Gray Eagle” unmanned aircraft relies on GPS to navigate. It has to – there is no pilot on board!

So, if you want to disrupt someone’s ability to target something with GPS – you can jam the signal.

This is not an empty threat – there have already been documented attacks on both military and civilian targets in the Middle East using these GPS guided weapons.

A GBU-32 Guided Bomb Unit being loaded on an F-35
GPS was invented originally for accurate navigation of vehicles and military units – but now it is so accurate it can be used to guide precision weapons. This is a GBU-32 GPS guided bomb.

By the way, if you are wondering – jamming GPS (or cell phones, or any other radio frequency) is highly illegal in the United States.

GPS Spoofing

OK, now we know that we can jam GPS devices with an earth-bound high powered transmitter – and render those devices useless.

But, there is also a more insidious possibility.

Various parties are working on GPS spoofing.

Rather than render the GPS receiver unusable, GPS spoofing is used to trick or deceive the device into showing an incorrect position.

In that case, the user of the device may think they are somewhere they are not.

GPS spoofing takes a lot more technical expertise than simple brute force jamming.

The spoofing transmitter has to “convince” the device that it’s signal is legitimate – and feed it false information that will jive with the devices configuration.

As a civilian, you probably don’t have much reason for concern.

For now, this is a nation-state and military level of technology.

But understand that this field of technology is part of the future of warfare and conflict.

In Summary

Satellite navigation systems like GPS are amazingly useful – to both civilians and the military.

But, because of their ease of use they can be jammed through brute force techniques – or spoofed to show an incorrect position.

What’s the takeaway?

Don’t rely solely on GPS for critical navigation – have a backup method.

Sometimes you just have to break out the old fashioned paper map and use some dead-reckoning.

GPS Spoofing – References

Wikipedia: Global Positioning System

Information about GPS Jamming – Any radio frequency jamming is illegal in the US. The jammer hardware is also illegal to make, or to sell.

GNSS Jamming and Spoofing, aka Galileo’s Authentication Algorithm Part 3

The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement.

The satnav system in a Tesla Model X SUV
Nearly every new car sold has a Satnav system. The nav system included in the Tesla Model X uses GPS. It makes driving directions so easy!