hardMultiple ChoiceObjective-mapped
Best Risk Response for Legacy Systems That Cannot Be Patched
An organization has a legacy system that cannot be patched due to vendor end-of-life. The system processes non-critical data. The risk manager has determined that the likelihood of exploitation is low, but the impact would be high. Which risk response strategy is MOST appropriate?
Quick Answer
The answer is to accept the risk with compensating controls such as network segmentation. This is the most appropriate risk response for legacy systems that cannot be patched because the system processes non-critical data and the likelihood of exploitation is low, yet the impact would be high. By isolating the legacy system through network segmentation, you reduce the attack surface and prevent a breach from spreading to critical assets, effectively lowering the likelihood without needing a patch. On the CRISC exam, this scenario tests your ability to balance risk appetite with practical controls—many candidates mistakenly choose decommissioning or insurance, but the key is that the data is non-critical and the risk is within tolerance, making acceptance with compensating controls the correct path. Remember the memory tip: “Isolate, don’t eliminate” for end-of-life systems that still serve a business purpose.
⚠ Common exam trap
ISACA often tests the misconception that 'high impact' always requires mitigation or avoidance, but the trap here is that when likelihood is low and the data is non-critical, acceptance with compensating controls is the most cost-effective and appropriate response per the risk management framework.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Accept the risk with compensating controls such as network segmentation.
The system processes non-critical data and cannot be patched, making risk acceptance with compensating controls the most appropriate strategy. Network segmentation reduces the likelihood of exploitation by isolating the legacy system from critical assets, while the low likelihood and non-critical data make decommissioning or insurance less suitable. This aligns with CRISC best practices for legacy systems where patching is impossible and the risk is within the organization's risk appetite.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Mitigate the risk by applying vendor patches.
Why it's wrong here
Patching is not possible for end-of-life systems.
- ✗
Avoid the risk by decommissioning the system immediately.
Why it's wrong here
May not be feasible if the system is still needed.
- ✗
Transfer the risk by purchasing cyber insurance.
Why it's wrong here
Insurance does not eliminate operational impact.
- ✓
Accept the risk with compensating controls such as network segmentation.
Why this is correct
Compensating controls reduce likelihood without patching.
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Same concept, more angles
2 more ways this is tested on CRISC
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A financial services company uses a legacy mainframe system for core banking transactions. The risk assessment identifies that the system does not support modern encryption standards, and data is transmitted in clear text over internal networks. The IT department has proposed implementing network segmentation and encryption at the application layer using a middleware solution. However, the cost is high and the project would take 18 months. Meanwhile, the company is planning to migrate to a new core system in two years. The risk appetite for data confidentiality is low. As the risk practitioner, what is the MOST appropriate risk response?
medium- ✓ A.Implement compensating controls such as strict network access controls and monitoring.
- B.Transfer the risk by purchasing cyber insurance covering data breach incidents.
- C.Accept the risk because the system will be replaced in two years.
- D.Avoid the risk by accelerating the migration to the new system within 18 months.
Why A: The correct response is to implement compensating controls such as strict network access controls and monitoring. Given the low risk appetite for data confidentiality, the 18-month delay for the middleware solution is unacceptable, and the two-year migration timeline leaves a significant exposure window. Compensating controls like VLAN segmentation, ACLs, and continuous traffic monitoring can reduce the likelihood of exploitation of the clear-text transmission without requiring changes to the legacy mainframe itself.
Variation 2. A company has identified that its legacy financial system has a high inherent risk due to outdated architecture. The system cannot be replaced for three years. What is the best risk treatment strategy?
medium- A.Accept the risk and allocate contingency funds for potential incidents.
- B.Transfer the risk by purchasing cyber insurance.
- C.Avoid the risk by discontinuing the system immediately.
- ✓ D.Implement compensating controls such as network segmentation and enhanced monitoring.
Why D: When a legacy system cannot be replaced for three years, the most effective risk treatment is to reduce the likelihood and impact of exploitation through compensating controls. Network segmentation limits lateral movement from the legacy system, and enhanced monitoring (e.g., SIEM with custom rules for anomalous traffic) provides early detection of compromise. This aligns with the ISACA risk treatment principle of risk reduction when avoidance or transfer is not feasible.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CRISC practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CRISC exam.