In the near future wireless sensor networks will be employed in a wide variety of applications establishing ubiquitous networks that will pervade society. The inherent vulnerability of these massively deployed networks to a multitude of threats, including physical tampering with nodes exacerbates concerns about privacy and security. For example, denial of service attacks (DoS) that compromise or disrupt communications or target nodes serving key roles in the network, e.g. sink nodes, can easily undermine the functionality as well as the performance delivered by the network. Particularly vulnerable are the components of the communications or operation infrastructure. Although, by construction, most sensor network systems do not possess a built-in infrastructure, a virtual infrastructure, that may include a coordinate system, a cluster structure, and designated communication paths, may be established post-deployment in support of network management and operation. Since knowledge of this virtual infrastructure can be instrumental for successfully compromising network security, maintaining the anonymity of the virtual infrastructure is a primary security concern. Somewhat surprisingly, in spite of its importance, the anonymity problem has not been addressed in wireless sensor networks. The main contribution of this work is to propose an energy-efficient protocol for maintaining the anonymity of the virtual infrastructure in a class of sensor network systems. Our solution defines schemes for randomizing communications such that the cluster structure, and coordinate system used remain undetectable and in visible to an observer of network traffic during both the setup and operation phases of the network.