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ISC2 CC Practice Question: A company deploys a new intrusion detection…
A company deploys a new intrusion detection system (IDS) on the internal network. Which of the following best describes the primary purpose of this system?
⚠ Common exam trap
ISC2 often tests the distinction between IDS and IPS, where candidates mistakenly assume an IDS can block traffic because they conflate detection with prevention.
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
✓
Detect and alert on potential security incidents.
An intrusion detection system (IDS) is a passive monitoring technology that analyzes network traffic or system activity for signs of malicious behavior or policy violations. Unlike an intrusion prevention system (IPS), an IDS does not take inline action to block traffic; its primary purpose is to detect suspicious activity and generate alerts for security personnel to investigate and respond.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Block malicious traffic in real time.
Why it's wrong here
An IDS detects and alerts on malicious activity; blocking traffic in real time is the function of an intrusion prevention system (IPS) placed inline. It is tempting because detection often precedes response, and an IPS would be correct where inline enforcement is required.
- ✓
Detect and alert on potential security incidents.
Why this is correct
An IDS passively inspects mirrored traffic and generates alerts on suspicious patterns, satisfying the detection requirement without sitting inline. It identifies and notifies; it does not block, which distinguishes it from an IPS. Prevention and quarantine fall outside its primary purpose.
- ✗
Encrypt sensitive data at rest.
Why it's wrong here
Encryption at rest is provided by disk, database or file-level encryption, not by an IDS, which inspects network traffic for signs of intrusion. It is tempting because both are security controls, and encryption would be correct for protecting stored data confidentiality.
- ✗
Prevent unauthorized access to the network.
Why it's wrong here
Preventing unauthorised access is the role of firewalls, access control and authentication; an IDS passively monitors and alerts rather than enforcing admission. It is tempting because IDS alerts support access security, and a firewall would be correct where traffic must be blocked.
Go deeper
Related to this question
Learn chapter
Network Security Foundations
Key term
Policy
A policy is a set of rules or guidelines that defines how an organization manages, secures, and operates its IT systems and services.
Key term
Intrusion Detection System
An Intrusion Detection System (IDS) is a security tool that monitors network traffic or system activities for malicious actions or policy violations and sends alerts to administrators.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC practice question is part of Courseiva's free ISC2 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 CC exam.