A system and method for gathering data regarding receivers of multicast content is provided. A spanning tree is used to connect a content producer, such as a pay-per-view broadcaster, to one or more receivers over a computer network, such as the Internet. Clients that wish to join a multicast group to which content is sent join the multicast group at the client's designated multicast router. The router sends information regarding the request, such as a tally of the number of clients that have joined the group, through intermediate routers to an endpoint router as identified by the spanning tree. The content producer is able to use the information, such as the tally and demographic information, to analyze the group of receivers. In a pay-per-view setting, the tally can further be compared to the number of subscribers to determine whether illicit receivers have joined the group, whereupon appropriate action is taken.