The threat and vulnerability of GPS

The critical reliance and important usage on GPS nowadays, both in civil and military, has recently brought up a hot discussion again for the concerns in its threat and vulnerability.

Anyhow, this issue is not new, and has been discussed among technology experts for many years. Just that when GPS usage become more and more widespread, its threat and vulnerability need to be brought to its users' awareness, especially in the military, government and business sectors.

The GPS operation relies on signals from some 30 over orbiting satellites surrounding the earth in the space. In order for a GPS receiver to triangulate its position on earth, it needs to get signals from at least 3 GPS satellites.

GPS signal is known to be exceptionally weak. Each satellite transmits a signal equivalent to the power of a 25W light bulb from an distance of about 20,000km away. Such a weak signal can be readily interfered with or denied by unintentional or deliberate radio wave interference.

Portable GPS jammer devices such as the one shown in the diagram below have been made available for quite some times.

Some car security system and transportation logistic system make use of GPS to keep track on the position of the vehicle. It has been reported that car thieves make use of GPS jammer to disrupt the GPS signal and defeat the vehicle tracking system, therefore render the vehicle unlocatable.

Employees who drive vehicles that are tracked by their companies can also make use of the GPS jammer to hide their tracks.


In Germany, it is believed that some drivers are using GPS jammer to evade GPS-based road charging system.

Robbers can also easily spoof the GPS signal and guide the target vehicle to drive to their trap location.

Imagine what would happen if terrorists make attack on the GPS function of air traffic and/or naval traffic.

Beside its global positioning function, GPS is also used as a time server for time synchronization in certain infrastructure. This function can also be defeated by the jammer, and time critical system could be hacked in this way.

The GPS signal used by the US military is different from the civil signal, and is encrypted. However, it is also vulnerable to GPS jammer and subjected to interferrance from the enemy.

Imagine a GPS dependent missle being mislead by the enemy to attack on wrong target, or worse still, to attack to ally target instead of the enemy.

By intercepting the GPS signal, the position of military GPS user could be exposed to the enemy.

In the video below, you can see the GPS jammer in action and how it defeated the civil and military GPS.



So, what can we do to minimize the threat to GPS? Beside waiting for the US to strengten on the signaling, when we want to make use of GPS, also use some other alternative methods so that GPS could not be a single point of failure.