CRISC IT Risk Assessment Practice Question
An organization implements an intrusion detection system (IDS) to monitor for security incidents. This is an example of which type of control?
⚠ Common exam trap
Candidates often confuse an IDS with an IPS (Intrusion Prevention System), which is a preventive control because it can actively block traffic, whereas the question specifically asks about an IDS, which is purely detective.
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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Detective
An intrusion detection system (IDS) is a detective control because it monitors network traffic or system activity for signs of malicious behavior or policy violations and generates alerts when such patterns are detected. Unlike preventive controls, an IDS does not block or stop the attack in real time; it only identifies and reports the incident for subsequent investigation and response.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Detective
Why this is correct
An IDS identifies and logs intrusions after they occur, satisfying the stem's requirement to monitor for security incidents. Detective controls discover and report events rather than preventing them, unlike preventive controls. This aligns with CRISC's control classification, where monitoring mechanisms are detective by definition.
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Corrective
Why it's wrong here
Corrective controls restore systems or data after an incident has occurred, such as backups or patch deployment. An IDS only detects and alerts on malicious activity; it takes no remedial action itself. Corrective would fit a scenario requiring recovery or repair after compromise, not continuous monitoring for incidents.
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Compensating
Why it's wrong here
A compensating control substitutes for a primary control that cannot be implemented, such as segregation of duties replaced by supervisory review. An IDS is not substituting for another control; it is the primary detective mechanism monitoring network activity for incidents.
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Preventive
Why it's wrong here
Preventive controls block or stop an event before it occurs, such as firewalls, access restrictions or encryption. An IDS only detects and alerts on suspicious activity after it happens, so it cannot prevent the incident itself.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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