Enter Greyball, an Uber program that's been nested under its broader "violation of terms of service" (VTOS) program since at least 2014. Greyball helped Uber identify undercover officers posing as riders in places like Portland -- where the Times reports Uber drivers were operating without the city's permission, prompting a crackdown. When Erich England, a code enforcement officer, attempted to use the app to hail a car, this happened, per the Times (our emphasis added):
But unknown to Mr. England and other authorities, some of the digital cars they saw in their Uber apps were never there at all. The Uber drivers they were able to hail also quickly canceled. That was because Uber had tagged Mr. England and his colleagues — essentially Greyballing them as city officials — based on data collected from its app and through other techniques. Uber then served up a fake version of its app that was populated with ghost cars, to evade capture.