The best course of action for a risk practitioner upon learning that a control under internal review may no longer be necessary is to obtain approval to retire the control. This will help to ensure that the control is removed in a controlled and documented manner, and that the relevant stakeholders are informed and agree with the decision. Retiring unnecessary controls can also help to optimize the control environment, reduce costs and complexity, and improve efficiency and performance. Updating the status of the control as obsolete, consulting the internal auditor for a second opinion, and verifying the effectiveness of the original mitigation plan are not the best courses of action, as they may not address the root cause of the control's obsolescence, and may delay or complicate the control retirement process. References = Risk and Information Systems Control Study Manual, 7th Edition, Chapter 3, Section 3.1.1.2, page 1071
1: ISACA Certified in Risk and Information Systems Control (CRISC) Exam Guide, Answer to Question
649.

Reviewing historical risk events is most useful for the risk assessment process within the risk management life cycle. Risk assessment is the process of identifying, analyzing, and evaluating the risks that may affect the project or the organization1. Reviewing historical risk events can help to:
* Identify the sources, causes, and consequences of past risks and learn from the successes and failures of previous projects or organizations
* Analyze the likelihood and impact of potential risks based on historical data and trends, and use statistical methods or models to estimate the probability and severity of risk scenarios
* Evaluate the level of risk exposure and compare it with the risk appetite and tolerance of the project or the organization, and prioritize the risks that need further attention or action
* Use historical risk events as inputs or examples for risk identification and analysis techniques, such as brainstorming, checklists, interviews, surveys, SWOT analysis, root cause analysis, or Monte Carlo simulation2 References = Risk and Information Systems Control Study Manual, Chapter 5: Risk Assessment Process3

The most important factor when reporting to senior management on changes in trends related to IT risk is materiality. Materiality is the extent to which the information reported is significant, relevant, and useful for decision-making purposes. Materiality helps to prioritize the most important risks and communicate them effectively to senior management12
1: Integrating KRIs and KPIs for Effective Technology Risk Management - ISACA 2: CRISC Review Manual, 7th Edition, page 271

The most reliable evidence of a control's effectiveness is a system-generated testing report. A system- generated testing report is a document that shows the results of automated tests performed by the system to verify that the control is functioning as intended and producing the expected outcomes. A system-generated testing report is reliable, because it is objective, consistent, accurate, and timely, and because it can provide a high level of assurance and confidence in the control's effectiveness. The other options are not as reliable as a system-generated testing report, although they may provide some evidence of the control's effectiveness. A risk and control self-assessment, senior management's attestation, and a detailed process walk-through are all examples of manual or subjective evidence, which may be prone to errors, biases, or inconsistencies, and which may provide a lower level of assurance and confidence in the control's effectiveness. References = Risk and Information Systems Control Study Manual, Chapter 3, Section 3.4.1, page 3-32.

Strong authentication is the most effective measure against external threats to an organization's confidential information. Confidential information is any data or information that is sensitive, proprietary, or valuable to the organization, and that should not be disclosed to unauthorized parties1. External threats are malicious actors outside the organization who attempt to gain unauthorized access to the organization's networks, systems, and data, using various methods such as malware, hacking, or social engineering2. Strong authentication is a method of verifying the identity and legitimacy of a user or device before granting access to the organization's resources or data3. Strong authentication typically involves the use of multiple factors or methods of authentication, such as passwords, tokens, biometrics, or certificates4. Strong authentication can prevent or reduce the risk of external threats to the organization's confidential information, by making it more difficult and costly for the attackers to compromise the credentials or devices of the authorized users, and by limiting the access to the data or resources that are relevant and necessary for the users' roles and responsibilities5. The other options are not the most effective measures against external threats to the organization's confidential information, as they are either less secure or less relevant than strong authentication. Single sign-on is a method of allowing a user to access multiple systems or applications with a single set of credentials, without having to log in separately for each system or application6. Single sign-on can improve the user experience and convenience, as well as reduce the administrative burden and cost of managing multiple accounts and passwords. However, single sign-on is not the most effective measure against external threats to the organization's confidential information, as it can also increase the risk of credential compromise or misuse, and create a single point of failure or attack for the attackers to access multiple systems or data. Data integrity checking is a method of ensuring that the data or information is accurate, complete, and consistent, and that it has not been altered or corrupted by unauthorized parties or processes.
Data integrity checking can involve the use of techniques such as checksums, hashes, digital signatures, or encryption. Data integrity checking can enhance the quality and reliability of the data or information, as well as detect and prevent any unauthorized or malicious changes or tampering. However, data integrity checking is not the most effective measure against external threats to the organization's confidential information, as it does not prevent or reduce the risk of data theft or leakage, and it does not verify the identity or legitimacy of the users or devices accessing the data. Intrusion detection system is a system that monitors the network or system activities and events, and detects and alerts any suspicious or malicious behaviors or anomalies that may indicate an attempted or successful breach or attack. Intrusion detection system can help to identify and respond to external threats to the organization's networks, systems, and data, by providing visibility and awareness of the network or system status and activities, and by enabling timely and appropriate actions or countermeasures. However, intrusion detection system is not the most effective measure against external threats to the organization's confidential information, as it is a reactive or passive system that does not prevent or block the attacks, and it may generate false positives or negatives that can affect its accuracy and efficiency. References = Risk and Information Systems Control Study Manual, 7th Edition, Chapter 4, Section
4.2.1, Page 189.