Is it possible to guard against GPS attacks?

[harlan4096]

Driving downtown, you glance at your navigation app and see that it thinks that you are at the airport. A bit unsettling, no doubt. This is not a made-up situation; it’s a real example of GPS spoofing — that is, the shift of GPS coordinates using a fake (but stronger) GPS signal from the ground that drowns out the one from the satellite.

Who’s doing it and why is a bit of a mystery, but this trick has numerous practical uses — from hijacking drones to interfering with yacht and tanker navigation systems. The only good news is that protection solutions are beginning to appear, albeit slowly.

For those in a hurry, here are the basic facts of GPS spoofing:

* GPS spoofing involves an attempt to deceive a GPS receiver by broadcasting a fake GPS signal from the ground. All navigators in the vicinity start showing the wrong location.

* GPS spoofing can be used to hijack UAVs and cars, or confuse taxi drivers, drones, and sailors.

* GPS spoofing tools are quite affordable — a few hundred dollars will buy everything required.

* Anti-GPS spoofing technology is being developed, but mainly for large systems, such as maritime navigation.

* The simplest (if inconvenient) way to protect your smartphone or tablet is to switch it to “battery-saving location mode,” whereby only Wi-Fi and cellular networks are used to determine your location, and GPS is disabled (this mode is unavailable on some devices).

And now some details for those wishing to dig a little deeper.

How GPS spoofing works

To understand why GPS can be faked at all, recall the general principles of satellite navigation. Here’s how it works: Suspended above the Earth in geostationary orbit are several satellite systems. They are American GPS, European Galileo, Russian GLONASS, and Chinese BeiDou.

Each satellite transmits a continuous radio signal containing the satellite code and the precise signal transmission time. Your phone or other navigator does not transmit anything at all, but simply receives these radio signals from space. By analyzing the exact receipt time of each signal, it is possible to calculate the distance from the GPS receiver to each of the satellites.

With a bit of math and a comparison of several such signals (at least three, but the more the merrier), the receiver can determine its precise location relative to the satellites. And because the coordinates of the satellites are known and unvarying, doing this calculation makes it possible to work out the location of the GPS receiver on the Earth’s surface.

The problem is that the satellite signals are attenuated by the time they hit terra firma — and the antennas of most receivers are not particularly sensitive. Therefore, just by siting a fairly powerful radio transmitter nearby and broadcasting a fake but technically sound GPS signal from it, it is easy to drown out the satellites and cause all GPS receivers in the area to compute the wrong coordinates.

At the same time, the receivers lack the technical means to determine the direction of the signal, so they do not know that the signal is coming from a completely different source. Even worse, GPS spoofing equipment is very inexpensive (about $300), and all of the programs needed are generally free. In other words, it’s not some complicated stuff accessible only by military or special services — almost anyone can do it.

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