An increase in false negatives would be of greatest concern when reviewing the performance of an organization's IDSs, because it means that the IDSs are failing to detect and alert on actual attacks that are occurring on the network. False negatives can lead to serious security breaches, data loss, reputational damage, and legal liabilities for the organization. False positives, on the other hand, are alerts that are triggered by benign or normal activities that are mistaken for attacks. False positives can cause annoyance, inefficiency, and desensitization, but they do not pose a direct threat to the security of the network. Therefore, a decrease in false positives would be desirable, and an increase in false positives would be less concerning than an increase in false negatives.
References = CISM Review Manual, 16th Edition, page 2231; Intrusion Detection Systems | NIST

Information security due diligence is the process of assessing the current state of information security in an organization, identifying any gaps, risks, or vulnerabilities, and estimating the costs and efforts required to remediate them. Performing information security due diligence prior to making the purchase is important to determine the security exposures that may affect the value, reputation, or liability of the organization, as well as the feasibility and compatibility of integrating the security systems and processes of the two organizations.
References = CISM Review Manual 2022, page 361; CISM Exam Content Outline, Domain 1, Task 1.22; Information Security Due Diligence Questionnair

A security policy is a formal statement of the rules and principles that govern the protection of information assets in an organization. A security policy defines the scope, objectives, roles and responsibilities, and standards of the information security program. A primary purpose of creating security policies is to implement management's security governance strategy, which is the framework that guides the direction and alignment of information security with the business goals and objectives. A security policy translates the management's vision and expectations into specific and measurable requirements and controls that can be implemented and enforced by the information security staff and other stakeholders. A security policy also helps to establish the accountability and authority of the information security function and to demonstrate the commitment and support of the senior management for the information security program.
References =
* CISM Review Manual 15th Edition, page 1631
* CISM 2020: IT Security Policies2
* CISM domain 1: Information security governance [Updated 2022]3
* What is CISM? - Digital Guardian4