Abstract: Cloud Computing provides a good model for the providers to deploy the computing infrastructure and applications on-demand. It offers greater flexibility to users by connecting to various computing resources and allowing access to IT enabled services. But it has the risk of privacy of user data and security. Thus security among the users of cloud is the most important concern. One of the security issue in cloud computing is data mining based attacks, which involves that the data can be analyzed continuously by an unanonymous person to get the valuable information. Using the single cloud provider this is a major problem among the clients in the cloud, because the outside attacker can analyze their data for a long time to gain the sensitive information. In this paper, we have given the data mining based attacks on cloud data and a method to prevent the attacks.