The answer is a network-based IDS/IPS. This is the correct choice because it operates by inspecting traffic at the network perimeter in real time, combining signature-based detection to catch known attack patterns with behavioral anomaly detection to spot deviations from normal baselines, enabling both detection and automatic blocking of malicious traffic. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of how network-based solutions differ from host-based ones—a common trap is choosing a host-based IDS/IPS, which only protects a single endpoint and lacks the network-wide visibility needed for automated blocking. Remember the key distinction: network-based systems sit inline and can drop packets, while host-based systems typically only alert. A useful memory tip is to think of the network-based IDS/IPS as a security guard at the building entrance, scanning everyone who walks in, whereas a host-based system is a guard stationed inside a single room.
CAS-004 Security Operations Practice Question
This CAS-004 practice question tests your understanding of security operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An organization wants to implement a solution that automatically detects and blocks malicious traffic based on known signatures and behavioral anomalies. Which of the following should be deployed?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Network-based IDS/IPS
A network-based IDS/IPS (Intrusion Detection/Prevention System) is designed to inspect network traffic in real time, using a combination of signature-based detection (matching known attack patterns) and behavioral/anomaly-based detection (identifying deviations from normal traffic baselines). This dual approach allows it to both detect and automatically block malicious traffic, fulfilling the organization's requirement directly.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Next-generation firewall with application control
Why it's wrong here
A firewall typically works at layers 3-4 and may not inspect application-layer anomalies effectively.
✗
Web application firewall (WAF)
Why it's wrong here
WAF only protects web applications.
✗
Security information and event management (SIEM) system
Why it's wrong here
SIEM is for log aggregation and analysis, not inline blocking.
✓
Network-based IDS/IPS
Why this is correct
IDS/IPS combined provides detection and prevention for known signatures and anomalies.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a next-generation firewall's application control with the deep packet inspection and behavioral analysis capabilities of a dedicated IDS/IPS, overlooking that NGFWs typically lack comprehensive signature-based threat detection for non-application-layer attacks.
Detailed technical explanation
How to think about this question
Network-based IDS/IPS systems operate by capturing packets via promiscuous mode on a network interface, reassembling flows, and comparing packet payloads against a signature database (e.g., Snort rules or Suricata's emerging threats rules) while also applying statistical models for anomaly detection, such as detecting sudden spikes in ICMP echo requests indicative of a Smurf attack. In a real-world scenario, an IPS can automatically drop a TCP connection upon detecting a known exploit like EternalBlue (SMBv1 vulnerability) by matching the signature and resetting the session, whereas a firewall would only block based on port or protocol, not the malicious payload.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Network-based IDS/IPS — A network-based IDS/IPS (Intrusion Detection/Prevention System) is designed to inspect network traffic in real time, using a combination of signature-based detection (matching known attack patterns) and behavioral/anomaly-based detection (identifying deviations from normal traffic baselines). This dual approach allows it to both detect and automatically block malicious traffic, fulfilling the organization's requirement directly.
What should I do if I get this CAS-004 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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