In this paper, a dynamic audit service is proposed for verifying the integrity of non trusted and outsourced storage. This audit service is constructed based on the techniques fragmentation, sampling randomly, and indexing hashing table, supporting provable updates to data stored in clouds and timely anomaly detection. In addition, probabilistic query and periodic verification methods are used for improving the performance of audit services. The experimental results not only validate the effectiveness of the approaches, but also show that an audit system verifies the integrity with lower computation overhead and requiring less extra storage for audit metadata. © 2016, International Journal of Pharmacy and Technology. All rights reserved.