The most effective control against phishing macro attacks is to disable macros in documents originating from external sources. This control directly neutralizes the attack vector by preventing the malicious macro from executing at the endpoint level, regardless of whether the phishing email bypasses the email filter. Since the macro is the mechanism that launches PowerShell commands, blocking its execution environment stops the attack before it can proceed, making it a preventive technical control. On the Certified Information Security Manager CISM exam, this scenario tests your ability to distinguish between detective controls like email filtering and preventive controls that address the root cause at the host level. A common trap is choosing stronger email filtering, but that fails to account for the filter being bypassed; the correct answer focuses on the execution environment. Remember the mnemonic “Macro Must Be Muzzled” to recall that disabling macros from external sources is the definitive endpoint defense against this attack chain.
CISM Incident Management Practice Question
This CISM practice question tests your understanding of incident management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
After a security incident, the incident response team identifies that the root cause was a phishing email that bypassed the email filter. The email contained a malicious macro that executed PowerShell commands. Which control would be MOST effective in preventing similar incidents in the future?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Disable macros in documents originating from external sources
Disabling macros in documents from external sources directly addresses the attack vector: the malicious macro that executed PowerShell commands. This control prevents the macro from running, regardless of the email filter's failure, by blocking the execution environment at the endpoint level. It is a preventive technical control that stops the attack before it can proceed.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Implement network segmentation for sensitive systems
Why it's wrong here
Segmentation limits lateral movement, not initial infection.
✓
Disable macros in documents originating from external sources
Why this is correct
This directly prevents the attack vector used in the incident.
Related concept
Read the scenario before looking for a memorised answer.
✗
Deploy additional antivirus software on endpoints
Why it's wrong here
Antivirus may not detect zero-day malware.
✗
Conduct security awareness training for all employees
Why it's wrong here
Training reduces risk but does not fully prevent macro-based attacks.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose security awareness training (D) because it seems like a broad solution, but the question asks for the 'most effective' control against a specific technical attack vector, and disabling macros is a direct technical prevention that does not rely on human behavior.
Detailed technical explanation
How to think about this question
Microsoft Office applications use a Trust Center setting to control macro execution; disabling macros for documents from external sources (e.g., via Group Policy or registry keys like HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Word\Security\VBAWarnings) forces the application to block all macros from untrusted locations. This bypasses the need for user judgment because the macro code never runs, even if the user enables content, unless the document is explicitly trusted. In real-world scenarios, attackers often use social engineering to trick users into enabling macros, making this control critical for preventing PowerShell-based payloads like those used in Emotet or Dridex campaigns.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Incident Management — This question tests Incident Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Disable macros in documents originating from external sources — Disabling macros in documents from external sources directly addresses the attack vector: the malicious macro that executed PowerShell commands. This control prevents the macro from running, regardless of the email filter's failure, by blocking the execution environment at the endpoint level. It is a preventive technical control that stops the attack before it can proceed.
What should I do if I get this CISM question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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