Social engineering is a technique that involves manipulating or deceiving people into performing actions or divulging information that may compromise the security of an organization or its data12.
Entry into an organization's secured physical premises is a form of physical access that allows an unauthorized individual to access, steal, or damage the organization's assets, such as equipment, documents, or systems34.
The best way to prevent future occurrences of social engineering entry into an organization's secured physical premises is to conduct security awareness training, which is an educational program that aims to equip the organization's employees with the knowledge and skills they need to protect the organization's data and sensitive information from cyber threats, such as hacking, phishing, or other breaches56.
Security awareness training is the best way because it helps the employees to recognize and resist the common and emerging social engineering techniques, such as tailgating, impersonation, or pretexting, that may be used by the attackers to gain physical access to the organization's premises56.
Security awareness training is also the best way because it fosters a culture of security and responsibility among the employees, and encourages them to follow the best practices and policies for physical security, such as locking the doors, verifying the identity of visitors, or reporting any suspicious activities or incidents56.
The other options are not the best way, but rather possible measures or controls that may supplement or enhance the security awareness training. For example:
Employing security guards is a measure that involves hiring or contracting professional personnel who are trained and authorized to monitor, patrol, and protect the organization's premises from unauthorized access or intrusion78. However, this measure is not the best way because it may not be sufficient or effective to prevent or deter all types of social engineering attacks, especially if the attackers are able to bypass, deceive, or coerce the security guards78.
Installing security cameras is a control that involves using electronic devices that capture and record the visual images of the organization's premises, and provide evidence or alerts of any unauthorized access or activity .
However, this control is not the best way because it is reactive rather than proactive, and may not prevent or stop the social engineering attacks before they cause any harm or damage to the organization .
Requiring security access badges is a control that involves using physical or electronic cards that identify and authenticate the employees or authorized visitors who are allowed to enter the organization's premises, and restrict or deny the access to anyone else . However, this control is not the best way because it may not be foolproof or reliable to prevent or detect the social engineering attacks, especially if the attackers are able to steal, forge, or clone the security access badges . References =
1: What is Social Engineering? | Types & Examples of Social Engineering Attacks1
2: Social Engineering: What It Is and How to Prevent It | Digital Guardian2
3: What is physical Social Engineering and why is it important? - Integrity3603
4: What Is Tailgating (Piggybacking) In Cyber Security? - Wlan Labs4
5: What Is Security Awareness Training and Why Is It Important? - Kaspersky5
6: Security Awareness Training - Cybersecurity Education Online | Proofpoint US6
7: Security Guard - Wikipedia7
8: Security Guard Services - Allied Universal8
Security Camera - Wikipedia
Security Camera Systems - The Home Depot
Access Badge - Wikipedia
Access Control Systems - HID Global

Qualitative measures are methods of expressing risk levels using descriptive terms, such as high, medium, or low, based on subjective criteria, such as likelihood, impact, or severity. Qualitative measures are often used to identify and prioritize risks, and to communicate risk information to stakeholders1.
Residual risk is the level of risk that remains after the risk response has been implemented. Residual risk reflects the effectiveness and efficiency of the risk response, and the need for further action or monitoring2.
Emerging threats are new or evolving sources or causes of risk that have the potential to adversely affect the organization's objectives, assets, or operations. Emerging threats are oftencharacterized by uncertainty, complexity, and ambiguity, and may require innovative or adaptive risk responses3.
The best reason to use qualitative measures to express residual risk levels related to emerging threats is that qualitative measures are better able to incorporate expert judgment. Expert judgment is the opinion or advice of a person or a group of people who have specialized knowledge, skills, or experience in a particular domain or field. Expert judgment can help to:
Provide insights and perspectives on the nature and characteristics of the emerging threats, and their possible causes and consequences Assess the likelihood and impact of the emerging threats, and their interactions and dependencies with other risks Evaluate the suitability and effectiveness of the risk responses, and their alignment with the organization's risk appetite and tolerance Identify and recommend the best practices and lessons learned for managing the emerging threats, and for improving the risk management process45 Qualitative measures are better able to incorporate expert judgment than quantitative measures, which are methods of expressing risk levels using numerical or measurable values, such as percentages, probabilities, or monetary amounts. Quantitative measures are often used to estimate and analyze risks, and to support risk decision making1. However, quantitative measures may not be suitable or feasible for expressing residual risk levels related to emerging threats, because:
Quantitative measures require reliable and sufficient data and information, which may not be available or accessible for the emerging threats Quantitative measures rely on mathematical models and techniques, which may not be able to capture or reflect the complexity and uncertainty of the emerging threats Quantitative measures may create a false sense of precision or accuracy, which may not be justified or warranted for the emerging threats Quantitative measures may be influenced or manipulated by biases or assumptions, which may not be valid or appropriate for the emerging threats67 Therefore, qualitative measures are better able to incorporate expert judgment, which can enhance the understanding and management of the residual risk levels related to emerging threats.
The other options are not the best reasons to use qualitative measures to express residual risk levels related to emerging threats, but rather some of the advantages or disadvantages of qualitative measures. Qualitative measures require less ongoing monitoring than quantitative measures, because they are simpler and easier to apply and update. However, this does not mean that qualitative measures can eliminate or reduce the need for monitoring, which is an essential part of the risk management process. Qualitative measures are better aligned to regulatory requirements than quantitative measures, because they are more consistent and comparable across different domains and contexts. However, this does not mean that qualitative measures can satisfy or comply with all the regulatory requirements, which may vary depending on theindustry or sector. Qualitative measures are easier to update than quantitative measures, because they do not depend on complex calculations or formulas. However, this does not mean that qualitative measures can always reflect the current or accurate risk levels, which may change over time or due to external factors. References = Qualitative Risk Analysis vs. Quantitative Risk Analysis - ISACA Residual Risk - ISACA Emerging Threats - ISACA Expert Judgment - ISACA Expert Judgment in Project Management: Narrowing the Theory-Practice Gap Quantitative Risk Analysis - ISACA Quantitative Risk Analysis: A Critical Review
[CRISC Review Manual, 7th Edition]

The policy has not been approved by the organization's board should be of most concern, as it indicates a lack of governance and oversight for the organization's cybersecurity posture. The board is ultimately responsible for setting the strategic direction, objectives, and risk appetite of the organization, and for ensuring that the cybersecurity policy aligns with them. Without the board's approval, the policy may not reflect the organization's vision, mission, values, and culture, and may not be communicated, implemented, or enforced effectively. The board's approval also demonstrates the commitment and support of the senior management for the cybersecurity program, and enhances the accountability and responsibility of the stakeholders involved.
References:
*ISACA, Essential Functions of a Cybersecurity Program1
*ISACA, Cybersecurity: Based on the NIST Cybersecurity Framework2

The greatest security risk in this scenario is that data may be commingled with other tenants' data on the public cloud infrastructure. Data commingling occurs when data from different sources or customers are mixed together without proper segregation or encryption. This may result in data leakage, unauthorized access, or loss of confidentiality and integrity. Data commingling is a common challenge in public cloud environments, where multiple customers share the same physical resources and network. System downtime, infrastructure management, and cloud provider certification are also potential risks in this scenario, but they are not as great as data commingling. References = Risk and Information Systems Control Study Manual, 7th Edition, Chapter 5, Section 5.2.1.1, page 2451
1: ISACA Certified in Risk and Information Systems Control (CRISC) Exam Guide, Answer to Question
638.

The best way to ensure ongoing control effectiveness is to measure trends in control performance. This will help to monitor and evaluate how well the controls are achieving their objectives, and to identify any deviations or anomalies that may indicate control failures or weaknesses. Measuring trends in control performance also helps to provide feedback and assurance to the stakeholders and decision makers, and to support continuous improvement and optimization of the control environment. Establishing policies and procedures, periodically reviewing control design, and obtaining management control attestations are good practices, but they are not the best way to ensure control effectiveness. 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
650.