Hellbanning (aka ghost posting) essentially dupes someone into thinking a system is working for him/her when in fact things are being faked. From the NYT article: "The company [Uber] then served up a fake version of the app [to law enforcement], populated with ghost cars, to evade capture." The linked-to Quincy Larson article is more to this point, describing Greyball as a tool that allows Uber to "figure out who's likely a cop, then 'hell-ban' them from being able to use Uber."
You can buy them in most high street electronics shops and even in Tesco or Asda (Walmart).
"The way of the world is to praise dead saints and prosecute live ones." -- Nathaniel Howe