Wireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring. One of the primary concerns that hinder the successful deployment of WSNs is source-location privacy (SLP). The privacy of the source location is vital and highly jeopardized by the usage of wireless communications. Although message content privacy can be ensured through message encryption, it is much more difficult to adequately address the SLP. For WSNs, SLP service is further complex by the fact that sensors consist of low-cost and energy-efficient radio devices. Therefore, using computationally intensive cryptographic algorithms (such as public-key cryptosystems) and large-scale broadcasting-based protocols are not suitable for WSNs. In this paper, we analyze the quantitatively measure source-location information leakage in routing-based SLP protection schemes for WSNs. Through this model, we identify vulnerabilities of some well-known SLP protection schemes. We also propose a routing technique, called the Sink Toroidal Region (STaR), to provide adequate SLP with low energy consumption. With this routing technique, the source node randomly selects an intermediate node within a designed STaR area located around the sink node. Furthermore, this routing protocol ensures that the intermediate node is neither too close, nor too far from the sink node in relations to the entire network. While ensuring SLP, our simulation results show that the proposed scheme is very efficient and can be used for practical applications. Copyright © 2012 John Wiley & Sons, Ltd.