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As wide applications of wireless sensor networks, privacy concerns have emerged as the main obstacle to success. When wireless sensor networks are used to monitor sensitive objects, the privacy about monitored object' locations becomes an important issue. When a sensor node reports a monitored object to base station by sending a series of packets through multiple hops, an adversary may trace back the source's location. Flooding-based phantom has a problem that message latencies become larger and energy costs become higher for protecting source-location privacy. In this paper, DROW (directed random walk) is proposed to make it difficult for an adversary to backtrack hop-by-hop to the origin of the sensor communication. In DROW, the source sensor sends out a packet, the packet is unicasted to its parent node. When intermediate node receives a packet, it forwards to one of its parent nodes in a directed random fashion. Compared to flooding-based phantom, DROW has smaller message latencies and lower energy costs. Especially, DROW has better safety period when intermediate node has multi-parent node.