Location awareness for wireless sensor networks has attracted significant interests in recent years. In hostile environments, there may be malicious attacks to mislead the location estimation of target nodes. In this paper, we propose a novel secured localization method by applying cooperative semi-definite programming (SDP) algorithm. We also introduce residual normalization to improve the SDP approximation. Cooperation enhances the capability to identify the compromised anchors and the accuracy of location estimation. SDP improves the reliability of the algorithm and the out-of-convex-hull performance. Simulation results are provided to demonstrate the aforementioned improvements.