1 Introduction
Data stored in databases is often critical to the organization's operations and also sensitive, for example with respect to privacy. Therefore, securing data stored in a database is a critical requirement. Data must be protected not only from external attackers, but also from users within the organizations [1]. A wide range of institutions from government agencies (e.g., military, judiciary etc.) to commercial enterprises are witnessing attacks by insiders at an alarming rate. The most important objective of these insiders is to either exfiltrate sensitive data (e.g., military plans, trade secrets, intellectual property, etc.) or maliciously modify the data for deception purposes or for attack preparation [2], [3], [4].