When developing a categorization method for security incidents, the categories must have agreed-upon definitions. This means that the categories should be clear, consistent, and understandable for all the parties involved in the incident response process, such as the incident handlers, the stakeholders, the management, and the external authorities. Having agreed-upon definitions for the categories can help to ensure that the incidents are classified and reported accurately, that the appropriate actions and resources are allocated, and that the communication and coordination are effective. Aligning with industry standards, creating by the incident handler, and aligning with reporting requirements are not mandatory for developing a categorization method for security incidents, although they may be desirable or beneficial depending on the context and objectives of the organization. Aligning with industry standards can help to adopt best practices and benchmarks for incident response, but it may not be feasible or suitable for all types of incidents or organizations. Creating by the incident handler can allow for flexibility and customization of the categories, but it may also introduce inconsistency and ambiguity if the definitions are not shared or agreed upon by others. Aligning with reporting requirements can help to comply with legal or contractual obligations, but it may not cover all the aspects or dimensions of the incidents that need to be categorized. References = CISM Review Manual, 16th Edition, pages 200-2011; CISM Review Questions, Answers & Explanations Manual, 10th Edition, page 822

When developing a categorization method for security incidents, the categories MUST have agreed-upon definitions. This is because having clear and consistent definitions for each category of incidents will help to ensure a common understanding and communication among the incident response team and other stakeholders. It will also facilitate the accurate and timely identification, classification, reporting and analysis of incidents. Having agreed-upon definitions will also help to avoid confusion, ambiguity and inconsistency in the incident management process