= Testing response scenarios is the most important factor in increasing the effectiveness of incident responders, as it allows them to practice their skills, identify gaps and weaknesses, evaluate the adequacy and feasibility of the incident response plan, and improve their coordination and communication. Testing response scenarios can also help to enhance the confidence and readiness of the incident responders, as well as to measure their performance and compliance with the policies and procedures. Testing response scenarios can be done through various methods, such as tabletop exercises, simulations, drills, or full-scale exercises, depending on the scope, objectives, and complexity of the scenarios.
The other options are not as important as testing response scenarios, although they may also contribute to the effectiveness of incident responders. Communicating with the management team is important to ensure that the incident responders have the necessary support, resources, and authority to carry out their tasks, as well as to report the status and outcomes of the incident response. However, communication alone is not sufficient to increase the effectiveness of incident responders, as they also need to have the relevant knowledge, skills, and experience to handle the incidents. Integrating staff with the IT department may help to facilitate the collaboration and information sharing between the incident responders and the IT staff, who may have the technical expertise and access to the systems and data involved in the incidents. However, integration alone is not enough to increase the effectiveness of incident responders, as they also need to have the appropriate roles, responsibilities, and processes to manage the incidents. Reviewing the incident response plan annually is important to ensure that the plan is updated and aligned with the current risks, threats, and business requirements, as well as to incorporate the lessons learned and best practices from previous incidents. However, reviewing the plan alone is not enough to increase the effectiveness of incident responders, as they also need to test and validate the plan in realistic scenarios and conditions. Reference = CISM Review Manual, 16th Edition, ISACA, 2022, pp. 223-225, 230-231.
CISM Questions, Answers & Explanations Database, ISACA, 2022, QID 1004.

Explanation
The development phase is the stage of the system development life cycle (SDLC) where the system requirements, design, architecture, and implementation are performed. The development phase is most challenging to implement security controls because it involves complex and dynamic processes that may not be well understood or documented. Security controls are essential for ensuring the confidentiality, integrity, and availability of the system and its data, as well as for complying with regulatory and contractual obligations. However, security controls may also introduce additional costs, risks, and constraints to the development process, such as:
Increased complexity and overhead of testing, verification, validation, and maintenance Reduced flexibility and agility of changing requirements or design Increased dependency on external vendors or third parties for security services or products Increased vulnerability to errors, defects, or vulnerabilities in the code or configuration Increased difficulty in measuring and reporting on security performance or effectiveness Therefore, implementing security controls in the development phase requires careful planning, coordination, communication, and collaboration among all stakeholders involved in the SDLC. It also requires a clear understanding of the security objectives, scope, criteria, standards, policies, procedures, roles, responsibilities, and resources for the system. Moreover, it requires a proactive approach to identifying and mitigating potential threats or risks that may affect the security of the system.
References = CISM Manual1, Chapter 3: Information Security Program Development (ISPD), Section 3.1:
System Development Life Cycle (SDLC)2
1: https://store.isaca.org/s/store#/store/browse/cat/a2D4w00000Ac6NNEAZ/tiles 2:
https://store.isaca.org/s/store#/store/browse/cat/a2D4w00000Ac6NNEAZ/tiles

Role-based access control (RBAC) is a policy-neutral access control mechanism that assigns access privileges to defined roles in the organization and then makes each user a member of the appropriate roles. RBAC reduces security administration efforts by simplifying the management of access rights across different users and resources. RBAC also enables consistent and efficient enforcement of the principle of least privilege, which grants users only the minimum rights required to perform their assigned tasks. RBAC can also facilitate the implementation of separation of duties, which prevents users from having conflicting or incompatible responsibilities. RBAC is among the most widely used methods in the information security tool kit1. Reference = CIS Control 6: Access Control Management - Netwrix, CISSP certification: RBAC (Role based access control), What is RBAC? (Role Based Access Control) - IONOS

A security policy is a general statement to define management objectives with respect to security. The security strategy addresses higher level issues. Guidelines are optional actions and operational tasks. A security baseline is a set of minimum requirements that is acceptable to an organization.

Explanation
This is the most urgent and effective action to prevent further damage or compromise of the organization's network and data. The other options are less important or irrelevant in this situation.
According to How to identify suspicious insider activity using Active Directory, one of the steps to detect and respond to suspicious activity is to isolate the affected device from the network. This can be done by disabling the network adapter, unplugging the network cable, or blocking the device's IP address on the firewall1. This will prevent the device from communicating with any malicious actors or spreading malware to other devices on the network.
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