Obviously country may vary, also, legality of the porn in question.

Typically ISPs don’t police activity themselves. IP Owners may hire people to monitor torrents send them a list all the IPs seeding, then they send a notice to the ISP that owns your IP address. Then your ISP will send you a “please stop, if you are caught 2 more times we’re canceling your service” letter.

Of course, if you are downloading CSAM or something, then law enforcement may do any number of responses.