How does leaverbuster work?

I've had a few games where people die a few times early game or for whatever reason and decide to quit. That's not the problem though; they don't leave or feed or quit or flame. They just run around the base from the fountain to the inner turret just outside the base, then across the map from top to bot and repeat so they won't get an afk notice or a feeding notice and there's no report category for that. Someone said leaverbuster detects this but I'm not sure. Can someone tell me how one would trigger it?