In a distributed web service integration environment, the selection of web services should be based on their reputation and quality-of- service (QoS). Various trust models for web services have been proposed to evaluate the reputation of web services/service providers. Current mechanisms are based on tracing the feedbacks to the past behaviors of web services. However, very few of them consider the robustness and attackresiliency of the trust models. In this paper, we present an attack resilient distributed trust management system in a web service management environment. The proposed attack resilient trust model uses two vectors to capture the behavior and the trustworthiness of a web service/service provider based on our analysis on the possible attacks against the trust models. We also present a set of experiments that show the effectiveness of our trust model in detecting malicious behavior of service providers.