Network coding has emerged some exciting future because of its smart technology in wireless sensor networks. At the same time, it is facing security attacks, especially conspiracy Attack. Most existing security strategies are concentrated on coding design, there has been almost no consideration from topological structure. In this background, a weakly-secure scheme is proposed from the perspective of topology. Considering the performance of this scheme, an advanced scheme is put forward later. Simulations show that the two strategies can prevent cooperative eavesdroppers from acquiring any useful information transmitted from source node to sink node and the performance of advanced scheme is better. Copyright © 2013 John Wiley & Sons, Ltd.