CAS-004 Governance, Risk, and Compliance Practice Question
Which security metric measures the average time it takes to detect a security incident after it has occurred?
⚠ Common exam trap
The trap is the overlapping 'MTTR' acronyms — candidates must distinguish Mean Time to Respond from Mean Time to Recover, and not confuse either with detection (MTTD).
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
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Mean Time to Detect (MTTD)
Mean Time to Detect (MTTD) is the metric that specifically measures the average elapsed time between when a security incident actually occurs and when it is detected by monitoring, alerting, or analyst investigation. It is a core SOC efficiency metric used to evaluate detection capabilities.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Mean Time to Detect (MTTD)
Why this is correct
Mean Time to Detect measures the average elapsed time between an incident occurring and its detection, exactly matching the metric described. It isolates detection speed from response or resolution timing, which are covered by separate metrics.
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Mean Time Between Failures (MTBF)
Why it's wrong here
MTBF measures the average elapsed time between failures of a component or system, describing reliability rather than detection speed. It is tempting because it is a widely quoted availability metric, but it is the correct choice when assessing hardware reliability, not incident detection latency.
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Mean Time to Respond (MTTR)
Why it's wrong here
MTTR measures time from detection to resolution, not detection itself; the stem asks for the metric ending when an incident is identified. It is tempting because MTTR is a headline incident-response KPI, and it would be the right answer if the question asked how quickly teams remediate after detection.
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Mean Time to Recover (MTTR)
Why it's wrong here
MTTR measures the average time to restore service after an incident, covering recovery rather than detection. It is tempting because it is a headline incident metric, but it is the correct choice when the question asks how quickly systems are repaired, not how quickly incidents are identified.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.