Requiring documentation that the finding will be addressed within the new system is the best course of action for a follow-up audit. An IS auditor should obtain evidence that the complex security vulnerability of low risk will be resolved in the new system and that there is a reasonable timeline for its implementation. The other options are not appropriate courses of action, as they may be too costly, time-consuming, or impractical for a low-risk finding. References:
* CISA Review Manual (Digital Version), Chapter 2, Section 2.5.31
* CISA Review Questions, Answers& Explanations Database, Question ID 209

The greatest impact as a result of the ongoing deterioration of a detective control is an increased number of false negatives in security logs. A detective control is a control that monitors and identifies any deviations or anomalies from the expected or normal behavior or performance of a system or process. A security log is a record of events or activities that occur within a system or network, such as user access, file changes, system errors, or security incidents. A false negative is a situation where a security log fails to detect or report an actual deviation or anomaly that has occurred, such as an unauthorized access, a malicious modification, or a security breach. An increased number of false negatives in security logs can have a significant impact on the organization's security posture and risk management, because it can prevent timely detection and response to security threats, compromise the accuracy and reliability of security monitoring and reporting, and undermine the accountability and auditability of user actions and transactions. The other options are not as impactful as anincreased number of false negatives in security logs, because they either do not affect the detection capability of a detective control, or they have less severe consequences for security management. References: CISA Review Manual (Digital Version)1, Chapter 5, Section 5.2.1

Allowing only corporate IM solutions is the best control to mitigate the malware risk associated with an IM system, because it can prevent unauthorized or malicious IM applications from accessing the network and infecting the system with malware. Corporate IM solutions can also enforce security policies and standards, such as encryption, authentication, and logging, to protect the IM system from malware attacks. Blocking attachments in IM, blocking external IM traffic, and encrypting IM traffic are also possible controls to mitigate the malware risk, but they are not as effective as allowing only corporate IM solutions. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.4.4

The first thing that should be done when an intrusion into an organization network is detected is to identify nodes that have been compromised. Identifying nodes that have been compromised is a critical step in responding to an intrusion, as it helps determine the scope, impact, and source of the attack, and enables the implementation of appropriate containment and recovery measures. The other options are not the first things that should be done when an intrusion into an organization network is detected, as they may be premature or ineffective without identifying nodes that have been compromised. Blocking all compromised network nodes is a containment measure that can help isolate and prevent the spread of the attack, but it may not be possible or feasible without identifying nodes that have been compromised. Contacting law enforcement is a reporting measure that can help seek external assistance and comply with legal obligations, but it may not be necessary or appropriate without identifying nodes that have been compromised. Notifying senior management is a communication measure that can help inform and escalate the incident, but it may not be urgent or accurate without identifying nodes that have been compromised. References: CISA Review Manual (Digital Version), Chapter 4, Section 4.2.2