Explanation
Unstructured data is data that does not have a predefined model or organization, making it difficult to store, process, and analyze using traditional relational databases or spreadsheets. Unstructured data can pose a risk to an organization if it contains sensitive, confidential, or regulated information that is not properly secured, managed, or governed. To minimize the risk of unstructured data, the first step is to identify the repositories of unstructured data, such as file servers, cloud storage, email systems, social media platforms, etc. This will help to understand the scope, volume, and nature of unstructured data in the organization, and to prioritize the areas that need further analysis and action. References: Unstructured data - Wikipedia

Explanation/Reference:
Explanation:
Attack attempts that could not be recognized by the firewall will be detected if a network- based intrusion detection system is placed between the firewall and the organization's network. A network-based intrusion detection system placed between the internet and the firewall will detect attack attempts, whether they do or do not enter the firewall.

This is because the follow-up of agreed corrective actions for reported audit issues should be done after the auditee has had enough time to implement the corrective actions and demonstrate their effectiveness and sustainability. The follow-up audit should not be too soon or too late, but based on a reasonable and realistic timeframe that allows for adequate testing and verification of the control operation12.
A). Progress updates indicate that the implementation of agreed actions is on track. is not the best answer, because progress updates are not sufficient to guide the follow-up audit timing. Progress updates are useful for monitoring and communicating the status and challenges of the corrective actions, but they do not provide conclusive evidence of the control operation. The follow-up audit should be based on actual results and outcomes, not on expectations or projections12.
C). Business management has completed the implementation of agreed actions on schedule. is not the best answer, because the completion of the implementation of agreed actions is not enough to guide the follow-up audit timing. The completion of the implementation only indicates that the auditee has taken the necessary steps to address the audit issues, but it does not guarantee that the corrective actions are effective and sustainable. The follow-up audit should be based on the evaluation and validation of the control operation, not on the completion of the control implementation12.
D). Regulators have announced a timeline for an inspection visit. is not the best answer, because the regulators' inspection visit is not relevant to guide the follow-up audit timing. The regulators' inspection visit is an external factor that may or may not coincide with the internal follow-up audit schedule. The follow-up audit should be based on the internal audit plan and objectives, not on the external audit requirements or expectations12.

Explanation
The best way to detect that a distributed denial of service (DDoS) attack is occurring is to use automated monitoring of logs. A DDoS attack disrupts the operations of a server, service, or network by flooding it with unwanted Internet traffic2. Automated monitoring of logs can help pinpoint potential DDoS attacks by analyzing network traffic patterns, monitoring traffic spikes or other unusual activity, and alerting administrators or security teams of any anomalies or malicious requests, protocols, or IP blocks3. Automated monitoring of logs can also help identify the source, type, and impact of the DDoS attack, and provide evidence for further investigation or mitigation.
The other options are not as effective as automated monitoring of logs for detecting DDoS attacks. Customer service complaints are an indirect and delayed indicator of a DDoS attack, as they rely on users reporting problems with accessing a website or service. Customer service complaints may also be caused by other factors unrelated to DDoS attacks, such as server errors or network issues. Server crashes are an extreme and undesirable indicator of a DDoS attack, as they indicate that the server has already been overwhelmed by the attack and has stopped functioning. Server crashes may also result in data loss or corruption, service disruption, or reputational damage. Penetration testing is a proactive and preventive measure for assessing the security posture of a system or network, but it does not detect ongoing DDoS attacks. Penetration testing may involve simulating DDoS attacks to test the resilience or vulnerability of a system or network, but it does not monitor real-time traffic or identify actual attackers.
References:
ISACA CISA Review Manual 27th Edition (2019), page 254
How to prevent DDoS attacks | Methods and tools | Cloudflare2
Understanding Denial-of-Service Attacks | CISA3

Section: Protection of Information Assets