How can they catch you?

yeah supposedly it costs around 5 grand to close one of these p2p copyright infringement lawsuits. Lets say someone downloads music from Limewire a lot, and deletes and rewrites any tags that come on audio files.How is it possible to get caught?The only way that I speculate it can happen is if your ISP decides to give your ip’s bandwith usage to the feds.Or is it more involved than that?thanks for any answers, and i dont post if you are going to suggest legal alternatives to p2p.so ISP’s have a log with everything that’s been downloaded?…and is it possible to be let off as a “minor”? The person in question is 16.