The most effective way to resolve the situation and define a comprehensive risk treatment plan would be to perform a root cause analysis. A root cause analysis is a method of identifying and addressing the underlying factors or causes that led to the occurrence of a problem or incident1. In this case, the problem or incident is the malware infection that affected the organization. By performing a root cause analysis, the organization can determine how and why the malware was able to infect the systems, what vulnerabilities or weaknesses were exploited, what controls orprocesses failed or were missing, and what actions or decisions contributed to the situation. A root cause analysis can help the organization to prevent or reduce the recurrence of similar incidents, as well as to improve the effectiveness and efficiency of the risk management process. A root cause analysis can also help the organization to define a comprehensive risk treatment plan, which is a set of actions or measures that are taken to modify the risk, such as reducing, avoiding, transferring, or accepting the risk2. Based on the findings and recommendations of the root cause analysis, the organization can select and implement the most appropriate risk treatment option for the malware risk, as well as for any other related or emerging risks. The risk treatment plan should also include the roles and responsibilities, resources, timelines, and performance indicators for the risk treatmentactions3. The other options are not the most effective ways to resolve the situation and define a comprehensive risk treatment plan, as they are either less thorough or less relevant than a root cause analysis. A gap analysis is a method of comparing the current state and the desired state of a process, system, or organization, and identifying the gaps or differences between them4. A gap analysis can help the organization to identify the areas of improvement or enhancement, as well as the opportunities or challenges for achieving the desired state. However, a gap analysis is not the most effective wayto resolve the situation and define a comprehensive risk treatment plan, as it does not address the causes or consequences of the malware infection, or the actions or measures to mitigate the risk. An impact assessment is a method of estimating the potential effects or consequences of a change, decision, or action on a process, system, or organization5. An impact assessment can help the organization to evaluate the benefits and costs, as well as the risks and opportunities, of a proposed or implemented change, decision, or action. However, an impact assessment is not the most effective way to resolve the situation and define a comprehensive risk treatment plan, as it does not investigate the origin or nature of the malware infection, or the solutions or alternatives to manage the risk. A vulnerability assessment is a method of identifying and analyzing the weaknesses or flaws in a process, system, or organization that can be exploited by threats to cause harm or loss6. A vulnerability assessment can help the organization to discover and prioritize the vulnerabilities, as well as to recommend and implement the controls or measures to reduce or eliminate them. However, a vulnerability assessment is not the most effective way to resolve the situation and define a comprehensive risk treatment plan, as it does not consider the root causes or impacts of the malware infection, or the risk treatment options or plans to address the risk. References = Risk and Information Systems Control Study Manual, 7th Edition, Chapter 2, Section 2.1.8, Page 61.