You only need to create filters for the routes you know, e.g. if you are an ISP providing internet connectivity for company X, then you know that the only adver

You only need to create filters for the routes you know, e.g. if you are an ISP providing internet connectivity for company X, then you know that the only advertisement from the link to X can be for X and if the link to company X advertises routes from Google, Facebook or Apple AS's, then that's bogus. It's just tedious to do this, and a lot of providers, especially smaller ones don't bother with it.