Abstract
One of the key applications that uses the knowledge discovered by data mining is called Chase. Chase is a process that replaces null or missing values with the values predicted by the knowledge, and it is mainly used to obtain more complete information systems or to replace unknown attribute values in user queries. The process improves the quality of query answers with increased volume of reliable data, and helps the system understand user queries that would otherwise be difficult. However, a security breach may occur when a set of data in an information system is confidential. The confidential data can be hidden from the public view. However, Chase has the capability to reveal the hidden data by classifying them as null or missing. In this paper, we discuss disclosure of confidential data by Chase and protection algorithms that reduce the risk. In particular, the proposed algorithms aim to protect confidential data with the least amount of additional data hiding.