The answer is to deploy a next-generation firewall (NGFW) with SSL/TLS inspection and application-level filtering. This is the correct choice because NGFW SSL inspection decrypts encrypted traffic at the network layer, allowing the firewall to analyze the payload for C2 traffic detection patterns that would otherwise be hidden by TLS encryption. Once decrypted, application-level filtering applies granular rules to identify and block the specific protocols or behaviors used by command-and-control channels, such as non-standard HTTP headers or beaconing intervals. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of how to defeat encrypted C2 evasion—a common trap is choosing a web proxy or IDS, which lack the deep packet inspection and inline blocking at the network layer that an NGFW provides. Remember the mnemonic: **NGFW = Network-layer decryption + Granular Filtering + Wire-speed blocking**.
CAS-004 Security Engineering Practice Question
This CAS-004 practice question tests your understanding of security engineering. 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.
A security engineer needs to implement a solution that will detect and block command-and-control (C2) traffic from malware on the internal network. The solution must be able to inspect encrypted traffic and operate at the network layer. Which of the following is the BEST choice?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy a next-generation firewall (NGFW) with SSL/TLS inspection and application-level filtering.
A next-generation firewall (NGFW) with SSL/TLS inspection and application-level filtering is the best choice because it can decrypt and inspect encrypted C2 traffic at the network layer, then apply application-aware rules to block malicious communications. This directly addresses the requirement to detect and block C2 traffic that uses encryption to evade traditional inspection.
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.
✗
Implement a web application firewall (WAF) to filter outbound HTTP/HTTPS traffic.
Why it's wrong here
WAF is designed for web application attacks and may not detect non-HTTP C2 traffic.
✗
Install a network-based intrusion detection/prevention system (IDS/IPS) with signature updates.
Why it's wrong here
Without decryption, encrypted C2 traffic would pass through undetected.
✗
Use endpoint detection and response (EDR) agents on all workstations and servers.
Why it's wrong here
EDR is host-based, not network-layer, and may not block traffic before it leaves the host.
✓
Deploy a next-generation firewall (NGFW) with SSL/TLS inspection and application-level filtering.
Why this is correct
NGFW can decrypt SSL/TLS traffic and inspect it for C2 patterns, then block malicious flows.
Clue confirmation
The clue word "best" in the question point toward this answer.
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 choose a network-based IDS/IPS (Option B) thinking it can inspect encrypted traffic, but without SSL/TLS decryption, it can only see encrypted payloads and cannot detect C2 commands hidden inside the encrypted tunnel.
Detailed technical explanation
How to think about this question
NGFWs perform deep packet inspection (DPI) by terminating TLS connections, decrypting the payload, applying application-level signatures (e.g., for protocols like DNS, HTTP/2, or custom C2 protocols), and then re-encrypting the traffic if allowed. In a real-world scenario, malware like TrickBot uses HTTPS to mimic legitimate traffic, and an NGFW with SSL inspection can detect the beaconing pattern or malicious payload even when the traffic is encrypted.
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 Engineering — This question tests Security Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy a next-generation firewall (NGFW) with SSL/TLS inspection and application-level filtering. — A next-generation firewall (NGFW) with SSL/TLS inspection and application-level filtering is the best choice because it can decrypt and inspect encrypted C2 traffic at the network layer, then apply application-aware rules to block malicious communications. This directly addresses the requirement to detect and block C2 traffic that uses encryption to evade traditional inspection.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This CAS-004 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-004 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.