A SIEM system is the best tool for providing an incident response team with the greatest insight into insider threat activity across multiple systems because it can collect, correlate, analyze, and report on security events and logs from various sources, such as network devices, servers, applications, and user activities. A SIEM system can also detect and alert on anomalous or suspicious behaviors, such as unauthorized access, data exfiltration, privilege escalation, or policy violations, that may indicate an insider threat. A SIEM system can also support forensic investigations and incident response actions by providing a centralized and comprehensive view of the security posture and incidents.
References: The CISM Review Manual 2023 defines SIEM as "a technology that provides real-time analysis of security alerts generated by network hardware and applications" and states that "SIEM systems can help identify insider threats by correlating user activity logs with other security events and detecting deviations from normal patterns" (p. 184). The CISM Review Questions, Answers & Explanations Manual 2023 also provides the following rationale for this answer: "A security information and event management (SIEM) system is the correct answer because it can provide the most insight into insider threat activity across multiple systems by collecting, correlating, analyzing, and reporting on security events and logs from various sources" (p. 95). Additionally, the Detecting and Identifying Insider Threats article from the CISA website states that
"threat detection and identification is the process by which persons who might present an insider threat risk due to their observable, concerning behaviors come to the attention of an organization or insider threat team.
Detecting and identifying potential insider threats requires both human and technological elements" and that
"technological elements include tools such as security information and event management (SIEM) systems, user and entity behavior analytics (UEBA) systems, and data loss prevention (DLP) systems, which can monitor, analyze, and alert on user activities and network events" (p. 1)1.