The answer is to implement client authentication and enable TLS encryption. This is the most effective immediate countermeasure because MQTT security without TLS authentication leaves both the transport layer and the broker’s access control completely open, allowing any client on the same network to subscribe to all topics and eavesdrop on sensitive IoT data. Enabling TLS provides transport-layer encryption and server verification, while client authentication (e.g., username/password or X.509 certificates) ensures only authorized devices can connect to the broker. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of IoT attack surfaces and the principle of defense in depth; a common trap is to suggest network segmentation alone, which does not prevent an attacker already on the same network. Remember the mnemonic “TLS + Auth = Trust” to recall that encryption and identity verification together close the two primary gaps in plain MQTT.
CEH Practice Question: Advanced Topics: Wireless, Cloud, IoT, Cryptography
This CEH practice question tests your understanding of advanced topics: wireless, cloud, iot, cryptography. 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 IoT device uses the MQTT protocol without any authentication or encryption. An attacker on the same network subscribes to all topics on the MQTT broker. Which of the following is the MOST effective immediate countermeasure?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement client authentication and enable TLS encryption
MQTT without authentication and encryption can be secured by enabling TLS for transport encryption and requiring credentials for clients. This prevents unauthorized access and eavesdropping.
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.
✗
Disable the MQTT broker entirely and switch to HTTP
Why it's wrong here
Switching protocols may not be feasible and does not address the core security issue.
✓
Implement client authentication and enable TLS encryption
Why this is correct
Correct. Enforcing authentication and TLS protects the MQTT communication from unauthorized access and sniffing.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the default topic names to obfuscated strings
Why it's wrong here
Obfuscation is not a security control; an attacker can still subscribe to all topics.
✗
Use a VPN for all IoT device communication
Why it's wrong here
A VPN adds overhead and may not be practical for all IoT devices; direct MQTT security is more efficient.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Advanced Topics: Wireless, Cloud, IoT, Cryptography — This question tests Advanced Topics: Wireless, Cloud, IoT, Cryptography — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement client authentication and enable TLS encryption — MQTT without authentication and encryption can be secured by enabling TLS for transport encryption and requiring credentials for clients. This prevents unauthorized access and eavesdropping.
What should I do if I get this CEH question wrong?
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An IoT device uses MQTT for communication. An attacker intercepts MQTT packets and observes that the publish messages are not encrypted and contain plaintext sensor data. Which of the following is the BEST recommendation to secure MQTT traffic?
medium
A.Base64-encode the payload
B.Switch to CoAP protocol
✓ C.Use MQTT over TLS
D.Implement a VPN on the device
Why C: MQTT itself does not provide encryption; using TLS (MQTT over TLS) encrypts the entire communication channel, protecting data in transit.
Variation 2. An IoT device uses the MQTT protocol without TLS. An attacker on the same network subscribes to all topics and captures messages. What is the MOST significant security risk?
medium
A.Firmware corruption
B.Denial of service
C.Replay attacks
✓ D.Loss of message confidentiality
Why D: Without TLS, MQTT traffic is sent in cleartext, allowing interception and reading of sensitive data.
Variation 3. An IoT device uses the MQTT protocol without TLS. An attacker on the same network captures messages and publishes a fake temperature reading. Which attack is being executed?
hard
A.Replay attack
B.Firmware reversing attack
✓ C.Man-in-the-middle attack
D.Denial of service attack
Why C: MQTT over plain TCP allows message interception and injection (man-in-the-middle) because no encryption or authentication is enforced.
Last reviewed: Jun 21, 2026
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.
This CEH practice question is part of Courseiva's free EC-Council 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 CEH 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.