Jon used a desktop computer attached to a GPS satellite simulator to create a fake GPS signal. Portable GPS satellite simulators can fit in the trunk of a car, and are often used for testing. They are available as commercial off-the-shelf products. You can also rent them for less than $1K a week -- peanuts to anyone thinking of hijacking a cargo truck and selling stolen goods.

In his first experiments, Jon placed his desktop computer and GPS satellite simulator in the cab of his small truck, and powered them off an inverter. The VAT used a second truck as the victim cargo truck. "With this setup," Jon said, "we were able to spoof the GPS receiver from about 30 feet away. If our equipment could broadcast a stronger signal, or if we had purchased stronger signal amplifiers, we certainly could have spoofed over a greater distance."

During later experiments, Jon and the VAT were able to easily achieve much greater GPS spoofing ranges. They spoofed GPS signals at ranges over three quarters of a mile. "The farthest distance we achieved was 4586 feet, at Los Alamos," said Jon. "When you radiate an RF signal, you ideally want line of sight, but in this case we were walking around buildings and near power lines. We really had a lot of obstruction in the way. It surprised us." An attacker could drive within a half mile of the victim truck, and still override the truck's GPS signals.