I think the way this works in practise is not that it's monitored by ISPs at the source but rather it's monitored at the other end of the connection.
What happens is that the copyright holder, or some company working on their behalf goes and connects to a torrent swarm.
Once they are connected to the swarm , they download the file in order to verify that it is in fact copyrighted material. At that point they can log any attempts by other peers to connect to them and download material from them since the clients have no real way of telling who is a normal peer and who is involved in monitoring.
They get a big list of IP addresses and times, from the IP they can figure out who the ISP is. They can then ask the ISP to release records for which subscriber was assigned that particular IP address at that time and bingo they have found the infringer.
- I believe there's some sort of issue with the approach where they log people who download from them, because if you download a copyrighted file being willfully shared by the copyright holder you haven't infringed.
- I once downloaded one song from a "500 greatest hits" type torrent. Some time later, my university sent me a notice that they'd received a complaint that I'd illegally downloaded Hotel California (I hadn't). Hotel California wasn't even adjacent in the torrent to the song I did download; there were never any attempts to get all or part of it. So the detection system (at that time, at least) would seem to leave something to be desired.
I'd be amazed if #1 washed in court. By connecting to a swarm that is distributing copyrighted works without the copyright holder's consent you've demonstrated that you have intent to pirate the material. Besides even if you argued that you got a few chunks of the file from the copyright holder (or a party acting on their behalf) you will have downloaded other chunks from others (and possibly uploaded some of them back to the rights holder).
#2 I'd put down to a random bureaucratic fuckup rather than an inherent issue with the detection system. I know a couple of people who've had letters from their ISPs regards these activities and they have said that they were accurate.
What happens is that the copyright holder, or some company working on their behalf goes and connects to a torrent swarm.
Once they are connected to the swarm , they download the file in order to verify that it is in fact copyrighted material. At that point they can log any attempts by other peers to connect to them and download material from them since the clients have no real way of telling who is a normal peer and who is involved in monitoring.
They get a big list of IP addresses and times, from the IP they can figure out who the ISP is. They can then ask the ISP to release records for which subscriber was assigned that particular IP address at that time and bingo they have found the infringer.