Some ISPs in Russia were doing the same (I don't know if they still do). The idea is that *.torrent files contain retracker.local in the list of trackers, this

Some ISPs in Russia were doing the same (I don't know if they still do). The idea is that *.torrent files contain retracker.local in the list of trackers, this tracker is local to each ISP and will respond with local peers.