Plagiarism Today outlines 6 steps to try and identify the person you should be sending “notice and take down” notices under the DMCA to.
Apart from complaints under the DMCA there could be some useful hints (apart from the inquiry to the Copyright Register) under our scheme. Although, of course, under reg. 20C the carriage service provider is supposed to publish those details in a prominent place on their website.
Read the suggestions here.