Commercial Flights Are Experiencing ‘Unthinkable’ GPS Attacks and Nobody Knows What to Do::New “spoofing” attacks resulting in total navigation failure have been occurring above the Middle East for months, which is “highly significant” for airline safety.
Edited my last comment, I don’t think that article goes into much detail. It only really covers the objections by GPS device manufacturers against LightSquared, not the technical aspect ie poor filtering by cheap GPS devices.
This article covers LightSquared’s claims of poor filtering by GPS devices: https://www.networkworld.com/article/696602/wireless-lightsquared-says-gps-makers-ignored-filtering-rules.html
This article also covers some of it: https://www.cnet.com/tech/mobile/lightsquared-blew-it-and-heres-why/
TL;DR GPS devices cut corners, however because they were established and so endemic across the industry, there was no practical way to fix them all and LightSquared was sent down the toilet.