The major concern with the situation where security incidents are resolved and closed, but root causes are not investigated, is that vulnerabilities have not been properly addressed. Vulnerabilities are weaknesses or gaps in the security posture of an organization that can be exploited by threat actors to compromise its systems, data, or operations. If root causes are not investigated, vulnerabilities may remain undetected or unresolved, allowing attackers to exploit them again or use them asentry points for further attacks. This can result in repeated or escalated security incidents that can cause more damage or disruption to the organization.
The other options are not as major as the concern about vulnerabilities, but rather secondary or related issues that may arise from the lack of root cause analysis. Abuses by employees have not been reported is a concern that may indicate a lack of awareness, accountability, or monitoring of insider threats. Lessons learned have not been properly documented is a concern that may indicate a lack of improvement, learning, or feedback from security incidents. Security incident policies are out of date is a concern that may indicate a lack of alignment, review, or update of security incident processes.
References:
* ISACA CISA Review Manual 27th Edition (2019), page 254
* Why Root Cause Analysis is Crucial to Incident Response (IR) - Avertium3
* Root Cause Analysis Steps and How it Helps Incident Response ...

The most effective method for detecting the presence of an unauthorized wireless access point on an internal network is A. Continuous network monitoring. This is because continuous network monitoring can capture and analyze all the wireless traffic in the network and identify any rogue or spoofed devices that may be connected to the network without authorization. Continuous network monitoring can also alert the system administrator of any suspicious or anomalous activities on the network and help to locate and remove the unauthorized wireless access point quickly.
Periodic network vulnerability assessments (B) can also help to detect unauthorized wireless access points, but they are not as effective as continuous network monitoring, because they are performed at fixed intervals and may miss some devices that are added or removed between the assessments. Review of electronic access logs can provide some information about the devices that access the network, but they may not be able to detect devices that use fake or stolen credentials or devices that do not generate any logs. Physical security reviews (D) can help to prevent unauthorized physical access to the network ports or devices, but they may not be able to detect wireless access points that are hidden or disguised as legitimate devices.

A black box penetration test is a type of security assessment that simulates an attack on a system or network without any prior knowledge of its configuration or architecture. The main objective of this test is to identify vulnerabilities and weaknesses that can be exploited by external or internal threat actors. To plan a black box penetration test, it is most important to ensure that the environment and penetration test scope have been determined. This means that the tester and the client organization have agreed on the boundaries, objectives, methods, and deliverables of the test, as well as the legal and ethical aspects of the engagement. Without a clear definition of the environment and scope, the test may not be effective, efficient, or compliant with relevant standards and regulations. Additionally, the tester may cause unintended damage or disruption to the client's systems or networks, or violate their privacy or security policies.
References:
* What are black box, grey box, and white box penetration testing?
* What Is Black-Box Penetration Testing and Why ShouldYou Choose It?

The first step that the organization should take to ensure that only the corporate network is used for downloading business data is to include a statement in its security policy about Internet use. A security policy is a document that defines the rules, expectations, and overall approach that an organization uses to maintain the confidentiality, integrity, and availability of its data1. A security policy should clearly state the acceptable and unacceptable use of Internet resources, such as personal accounts with ISPs, and the consequences of violating the policy. A security policy also helps to guide the implementation of technical controls, such as proxy servers, firewalls, or monitoring tools, that can enforce the policy and prevent or detect unauthorized Internet access.
The other options are not the first step that the organization should take, but rather subsequent or complementary steps that depend on the security policy. Using a proxy server to filter out Internet sites that should not be accessed is a technical control that can help implement the security policy, but it does not address the root cause of why users are using personal accounts with ISPs. Keeping a manual log of Internet access is a monitoring technique that can help audit the compliance with the security policy, but it does not prevent or deter users from using personal accounts with ISPs. Monitoring remote access activities is another monitoring technique that can help detect unauthorized Internet access, but it does not specify what constitutes unauthorized access or how to respond to it.
References:
* ISACA CISA Review Manual 27th Edition (2019), page 247
* What is a Security Policy? Definition, Elements, and Examples - Varonis1