The activity that best identifies operational problems, security misconfigurations, and malicious attacks is periodic log reviews. Log reviews are the process of examining and analyzing the records of events or activities that occur on a system or network, such as user actions, system errors, security alerts, or network traffic. Periodic log reviews can help to identify operational problems, such as system failures, performance issues, or configuration errors, by detecting anomalies, trends, or patterns in the log data. Periodic log reviews can also help to identify security misconfigurations, such as weak passwords, open ports, or missing patches, by comparing the log data with the security policies, standards, or baselines. Periodic log reviews can also help to identify malicious attacks, such as unauthorized access, data breaches, or denial of service, by recognizing signs of intrusion, compromise, or exploitation in the log data. The other options are not the best activities to identify operational problems, security misconfigurations, and malicious attacks, but rather different types of activities. Policy documentation review is the process of examining and evaluating the documents that define the rules and guidelines for the system or network security, such as policies, procedures, or standards. Policy documentation review can help to ensure the completeness, consistency, and compliance of the security documents, but not to identify the actual problems or attacks. Authentication validation is the process of verifying and confirming the identity and credentials of a user or device that requests access to a system or network, such as passwords, tokens, or certificates. Authentication validation can help to prevent unauthorized access, but not to identify the existing problems or attacks. Interface testing is the process of checking and evaluating the functionality, usability, and reliability of the interfaces between different components or systems, such as modules, applications, or networks. Interface testing can help to ensure the compatibility, interoperability, and integration of the interfaces, but not to identify the problems or attacks. References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 7, p. 377; Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 7, p. 405.