hardMultiple Choice
CRISC Practice Question: A company's control monitoring shows that a…
A company's control monitoring shows that a detective control has been 100% effective for the past year. However, a recent incident revealed that a data breach went undetected for three months. What is the MOST likely cause?
⚠ Common exam trap
Watch out — candidates often confuse 'control effectiveness' (how often it works when triggered) with 'control coverage' (whether it is designed to detect the relevant risk), leading them to incorrectly choose monitoring frequency or log tampering instead of recognizing the design gap.
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
✓
The control was not designed to detect the type of breach that occurred.
The detective control was 100% effective based on monitoring data, but it failed to detect a data breach for three months. This indicates the control was not designed to detect the specific type of breach that occurred, such as an exfiltration via an encrypted tunnel or a non-standard protocol. A control can be perfectly effective against known patterns while being blind to novel or out-of-scope attack vectors, which is why option C is correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The control failure occurred but was not recorded.
Why it's wrong here
A control reporting 100% effectiveness while a breach went undetected for three months indicates the control never detected the activity, not that a failure went unlogged. The monitoring data reflects the control's designed scope, which evidently excluded this threat vector. Unrecorded failures would still show gaps in logs.
- ✗
The monitoring frequency was insufficient to detect the breach.
Why it's wrong here
Insufficient monitoring frequency would still eventually detect the breach within the monitoring interval, and the stem states the control was 100% effective, implying detections were recorded. Frequency is the correct consideration when controls work but run too infrequently relative to the risk window, not when records show no failures at all.
- ✓
The control was not designed to detect the type of breach that occurred.
Why this is correct
A detective control can operate exactly as designed yet still miss a breach if its detection logic does not cover that attack vector. The three-month gap indicates a design scope limitation, not control failure or monitoring error, so the breach type fell outside the control's intended coverage.
- ✗
The control monitoring logs were tampered with.
Why it's wrong here
Deliberate tampering with monitoring logs is a malicious, low-probability explanation; the stem gives no evidence of adversarial activity, only a discrepancy between reported effectiveness and an undetected breach. Tampering would be the likely cause where logs show gaps or inconsistencies indicating intentional manipulation.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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