Security remains as a concern in MANET. In case of multicast MANET it is even more challenging as most of the routing protocols have been proposed assuming that the nodes in MANET behave in a secure manner. In this paper we are outlining a secure novel multicast routing protocol named Secure Hypercube Based Team Multicast Routing Protocol (S-HTMRP) that deals with both multicast routing and packet forwarding. Significant attention has been recently devoted to develop secure on-demand routing protocols that defend against a variety of possible attacks on routing. This paper develops and proposes a trust model to secure the network from the rushing attack, a variety of denial of services attack that may exist in the MANET. An alternative idea of implementing distributive security mechanism by computing trust levels from the inherent knowledge of the network has been proposed here, along with randomized packet forwarding mechanism and combining it with a scalable routing architecture to get a resulting routing protocol for multicast MANET that is more secure. The routes calculated through this mechanism may not be optimal but certainly have an accurate measure of reliability in them. The routing protocol namely S-HTMRP that has been proposed in this paper outperforms the existing hypercube based team multicast routing protocol in presence of rushing attack.