The first step is to invoke the incident response plan to ensure a systematic, controlled, and compliant response to the security incident.
"The incident response plan should be activated immediately to investigate, contain, and resolve incidents of unauthorized access."
- CISM Review Manual 15th Edition, Chapter 4: Incident Management, Section: Incident Response Plan Execution* ISACA practice questions also reinforce that invoking the incident response plan is the essential first response to contain the breach.

"A successful security program requires management support and involvement. One of the key aspects of management support is to decide on the value of assets and the acceptable level of risk for them. This will help define the security objectives and priorities for the program. The other options are possible activities within a security program, but they are not as important as management decision on asset value."

= The most important reason to ensure information security is aligned with the organization's strategy is to optimize security risk management. Information security is not an isolated function, but rather an integral part of the organization's overall objectives, processes, and governance. By aligning information security with the organization's strategy, the information security manager can ensure that security risks are identified, assessed, treated, and monitored in a consistent, effective, and efficient manner1. Alignment also enables the information security manager to communicate the value and benefits of information security to senior management and other stakeholders, and to justify the allocation of resources and investments for security initiatives2. Alignment also helps to establish clear roles and responsibilities for information security across the organization, and to foster a culture of security awareness and accountability3. Therefore, alignment is essential for optimizing security risk management, which is the process of balancing the protection of information assets with the business objectives and risk appetite of the organization4. References = 1: CISM Exam Content Outline | CISM Certification | ISACA 2: CISM_Review_Manual Pages 1-30 - Flip PDF Download | FlipHTML5 3: CISM 2020: Information Security & Business Process Alignment 4: CISM Review Manual 15th Edition, Chapter 2, Section 2.1

= Information classification is the process of assigning appropriate labels to information assets based on their sensitivity and value to the organization. Information classification should be aligned with the business objectives and risk appetite of the organization, and should be reviewed periodically to ensure its accuracy and relevance. The information security manager is responsible for establishing and maintaining the information classification policy and procedures, as well as providing guidance and oversight to the data owners and custodians. Data owners are the individuals who have the authority and accountability for the information assets within their business unit or function. Data owners are responsible for determining the appropriate classification level and security controls for their information assets, as well as ensuring compliance with the information classification policy and procedures. Data custodians are the individuals who have the operational responsibility for implementing and maintaining the security controls for the information assets assigned to them by the data owners.
If the information security manager believes that information has been classified inappropriately, increasing the risk of a breach, the best action is to complete a risk assessment and refer the results to the data owners. A risk assessment is a systematic process of identifying, analyzing, and evaluating the risks associated with the information assets, and recommending appropriate risk treatment options. By conducting a risk assessment, the information security manager can provide objective and evidence-based information to the data owners, highlighting the potential impact and likelihood of a breach, as well as the cost and benefit of implementing additional security controls. This will enable the data owners to make informed decisions about the appropriate classification level and security controls for their information assets, and to justify and document any deviations from the information classification policy and procedures.
The other options are not the best actions for the information security manager. Refering the issue to internal audit for a recommendation is not the best action, because internal audit is an independent and objective assurance function that provides assurance on the effectiveness of governance, risk management, and control processes. Internal audit is not responsible for providing recommendations on information classification, which is a management responsibility. Re-classifying the data and increasing the security level to meet business risk is not the best action, because the information security manager does not have the authority or accountability for the information assets, and may not have the full understanding of the business context and objectives of the data owners. Instructing the relevant system owners to reclassify the data is not the best action, because system owners are not the same as data owners, and may not have the authority or accountability for the information assets either. System owners are the individuals who have the authority and accountability for the information systems that process, store, or transmit the information assets. System owners are responsible for ensuring that the information systems comply with the security requirements and controls defined by the data owners and the information security manager. References = CISM Review Manual, 16th Edition, ISACA, 2020, pp. 49-51, 63-64, 69-701; CISM Online Review Course, Domain 3:
Information Security Program Development and Management, Module 2: Information Security Program Framework, ISACA2