Spoofing GPS is not easy. Just knowing the signal format is only a beginning. Jamming is easy.

The University of Texas at Austin Radionavigation Laboratory recently demonstrated a spoof, takeover and redirection of a drone. A US military drone was captured intact by Iran last year using a spoof/redirection attack that induced the drone navigation system to land.

Spoofing currently requires only a few thousand dollars in equipment but needs considerable expertise. If the cost and skills needed come down and allow spoofing of civilian GPS from a distance of 100 feet or more by an unskilled attacker we may have a problem that dwarfs handheld lasers & airplanes.