In this paper, for a battlefield self-organizing network the security flaw of RTS/CTS handshake mechanism will be analyzed based on its hierarchical and clustering features. By utilizing the fact that Cluster-type structure is easily to lead to the false blocking problem, a Denial of Service attack method is proposed. In this method, the attacker utilizes the pair nodes to forge malicious information, and thus, the communications among the nodes in the same cluster are blocked. Moreover, a defense strategy against the proposed attack is presented. The simulations with NS-2.33 show that the throughput descends largely in the attacking state, and when the defense strategy is implemented, the situation that the throughput descends could be improved obviously.