CEH Practice Question: Advanced Topics: Wireless, Cloud, IoT, Cryptography

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Perform a denial of service on the broker

  Why it's wrong here

  Simply subscribing to a topic, even a wildcard, is a standard client operation and does not inherently lead to a denial of service on the MQTT broker. While a massive flood of connection requests or subscriptions from numerous clients could potentially overwhelm broker resources, the action described is merely a single subscription. A DoS attack typically requires a sustained, high-volume malicious traffic generation or exploitation of a specific vulnerability, which is not achieved by a basic subscription.

• ✓

  Eavesdrop on all MQTT communications

  Why this is correct

  Without TLS encryption, all MQTT communications are transmitted in plaintext over the network. By subscribing to the '#' wildcard topic, an attacker can receive every message published to the broker, effectively eavesdropping on all traffic. This allows the interception of sensitive data, operational commands, and device states, as the unencrypted protocol provides no confidentiality protection against network sniffers or malicious subscribers.

• ✗

  Inject malicious control commands

  Why it's wrong here

  Injecting malicious control commands requires the ability to *publish* messages to specific topics that the IoT devices are subscribed to, not merely subscribing to topics. While an attacker might gain insight into command structures by eavesdropping, publishing commands typically requires authentication and authorization to write to those topics. A simple subscription only grants read access to messages, preventing direct command injection.

• ✗

  Replay previously captured messages

  Why it's wrong here

  Replaying previously captured messages involves intercepting legitimate messages and then re-transmitting them later to trick the system into performing an action. While subscribing to '#' allows an attacker to *capture* messages, the act of *replaying* them is a distinct subsequent step that requires publishing capabilities. The immediate action of subscribing only facilitates observation, not the active re-transmission of data.

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