contacts the ISP that IP address a.b.c.d had accessed/served copyright
infringing data at date/time dd-mm-yyyy HH:mm providing some kind of
detail on how they figured that out.
That report is a 'strike' and gets forwarded to the user.
If that then happens 6 times they are blocked.
The ISP as such does not do any content inspection.
It is though assumed that some ISPs simply count bytes and that they do
some investigation themselves when you reach a certain bandwidth
threshold (it seems to correlate that copyright infringers are
downloading a lot more than normal webbrowsing users...)