> What if the site operators are unresponsive or cannot be contacted? This seems like only a minor problem. If people are unresponsive, then oh well, they tri

> What if the site operators are unresponsive or cannot be contacted? This seems like only a minor problem. If people are unresponsive, then oh well, they tried to tell you you're hacked. If the site owner cannot be determined, they can email your ISP. This seems to work well for "one of your customers is torrenting movies", and since every ISP is known by definition (thanks, IP addresses), it should be fairly straightforward to get that message to the actual customer. (Send it with the invoice; if the customer doesn't pay invoices, then it's easy to resolve the hacked site. You were shutting them off anyway.)