How do people who steal Dish\DirecTV get caught?

Yes I understand it’s illegal. I’m not asking how to do it.

A friend of mine was recently served with a letter from DirecTV who knew about what he was doing. How could they have found him?

A satellite is only a receiver. Connection is uni-directional. The satellite does NOT broadcast. Is there anyway they can track the RECEIVING of signals?

He did buy the equipment with his credit card some time ago, so thats my guess.