According to the CRISC Review Manual, activity logging and monitoring is the best way to manage the risk associated with malicious activities performed by database administrators (DBAs), because it enables the detection and prevention of unauthorized or inappropriate actions on the database. Activity logging and monitoring involves capturing and reviewing the activities of the DBAs, such as the commands executed, the data accessed or modified, the privileges used, and the time and duration of the sessions. Activity logging and monitoring can also provide an audit trail for accountability and forensic purposes. The other options are not the best ways to manage the risk, because they do not directly address the malicious activities of the DBAs.
Periodic access review is a control that verifies the appropriateness of the access rights granted to the DBAs, but it does not monitor their actual activities. Two-factor authentication is a control that enhances the security of the authentication process, but it does not prevent the DBAs from performing malicious activities once they are authenticated. Awareness training and background checks are controls that aim to reduce the likelihood of the DBAs engaging in malicious activities, but they do not guarantee their compliance or behavior. References = CRISC Review Manual, 7th Edition, Chapter 4, Section 4.1.3, page 166.