CEH Wireless, IoT and Cloud Security Practice Question
A security analyst notices unusual traffic from a smart thermostat to an external IP address. The thermostat is on a separate IoT VLAN. Which action should the analyst take to investigate and mitigate the threat?
⚠ Common exam trap
Many exam-takers choose Option A (disconnect) because it seems like an immediate containment step, but CEH emphasizes that disconnecting destroys forensic evidence and prevents further analysis, whereas a targeted firewall rule allows both mitigation and investigation.
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
✓
Create a firewall rule to block traffic from the thermostat's MAC address to the external IP.
Creating a firewall rule to block traffic from the thermostat's MAC address to the specific external IP is a targeted, least-disruptive mitigation. It preserves the IoT VLAN's functionality for other devices while stopping the suspicious communication. This approach allows the analyst to investigate further without losing visibility into the threat, as the thermostat remains on the network for forensic analysis.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disconnect the thermostat from the network.
Why it's wrong here
While immediately stopping potential malicious communication, disconnecting the device entirely is a highly disruptive measure that prevents further investigation into the nature and scope of the unusual traffic. This action removes the "patient zero" from the network, making it difficult to capture additional forensic data or understand the attack vector without a confirmed threat. A more targeted containment strategy is generally preferred for initial response.
- ✗
Block all outbound traffic from the IoT VLAN.
Why it's wrong here
Implementing a blanket block on all outbound traffic from the entire IoT VLAN is an overly broad and disruptive response. This action would indiscriminately disable legitimate functionality for all other Internet of Things devices within that segment, causing widespread operational impact without specifically addressing the identified suspicious thermostat. Targeted containment is crucial to minimize collateral damage and maintain essential services.
- ✗
Uninstall the companion app from the user's smartphone.
Why it's wrong here
Uninstalling the companion app from a user's smartphone is unlikely to resolve unusual traffic originating directly from the smart thermostat itself. The device's firmware or a compromised state is the more probable source of unauthorized outbound communication, independent of the mobile application's presence or functionality. This action misidentifies the primary point of compromise and fails to contain the actual threat originating from the device.
- ✓
Create a firewall rule to block traffic from the thermostat's MAC address to the external IP.
Why this is correct
Creating a specific firewall rule to block traffic originating from the thermostat's unique MAC address destined for the identified external IP address is a precise and effective containment strategy. This action immediately isolates the suspicious communication without impacting the functionality of other legitimate devices on the network or preventing further internal analysis of the compromised thermostat. It allows for targeted mitigation while preserving operational continuity and forensic evidence.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.