The idea behind GPS spoofing is that one or several surface antennas and
sources could be set up in such a way that they would produce believable
position data that would take a vessel off course. The problem with this
concept is that the person in charge of the GPS spoofing hardware has to know
exactly where the vessel is at all times to start with and other vessels some
distance away, and not very far from the target vessel would get contradicting
signals from the virtual satellites.
Software could be used to detect changes in position data that is inconsistent
with present course and recent data. And in most cases there would be a period
of very inconsistent signals from satellites and more obvious, signal
strengths.
Another way to limit spoofing is to use directional antennas that prevent
reception from near horizon signals. Or detect low angle signals and sound the
alarm or implement a means of ignoring those sources.
The problem very high tech systems are often defeated by low tech solutions.
Successful GPS spoofing would be very high tech.
Many high tech systems that the government had developed in the past have been
defeated by low tech methods. An example is the microwave system that is
intended to turn back rioters by inducing burning pain. It was defeated by
using thick wooden shields which absorbed the RF energy.
Human resourcefulness and determination often defeats technology in low tech
ways. And the more complex a system is the easier it is to defeat. “The more
they overtake the plumbing the easier it is to stop up the drain.”
Most discussions have been about wireless spoofing. However, the most reliable
way to do it would be an “inside job” where a device would be put on board and
patched in the antenna lead. The correct GPS data would be received by the
device and then it would produce a virtual constellation of satellites that
would direct the vessel off course. However, the programmer would have to know
the course that the pilot intended to take in the first place if his goal is to
take the vessel to a different destination.
73
Bill wa4lav
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