GPS Spoofing With $3000 Worth of Equipment and a Laptop
First time accepted submitter svartbjorn writes "Todd Humphreys and a team from the University of Texas proved the concept that a terrorist could take over the navigation of a ship or even a plane, making it appear to the crew that the ship was moving along a straight line course when in fact it was changing course under the control of the device. This raises some serious issues for this being used for terrorist purposes."
This is why ships still have gyros.
So the only vessels at risk are those with 100% vegetarian crews.
It's probably not too much of an issue then...