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.