CEH’s approach to suspected compromise aligns with an incident-handling mindset: containment first, then analysis and remediation. In IoT and OT-adjacent environments (smart city infrastructure, SCADA-like components, embedded controllers), CEH emphasizes that suspicious external communications and unexplained open ports may indicate compromise, misconfiguration, exposed management services, or implanted malware/backdoors. Because IoT endpoints often have limited logging and are difficult to reimage safely, the safest next step is to isolate the suspected device to prevent further data exfiltration, command-and-control activity, or lateral movement to other city systems.

Option A best matches CEH guidance: isolate the device and investigate its firmware, services, and configuration, including checking for unauthorized binaries, altered firmware images, insecure default services, and hardcoded credentials. This also preserves evidence and reduces the blast radius.

Option C (blocking the external IP) can be helpful, but it’s a partial control: attackers can rotate infrastructure, and the device could still be compromised internally. Option B (full network pen test) is too broad and delays containment when a specific high-risk indicator is already present. Option D (attempting a reverse connection) crosses into active exploitation behavior and is not an appropriate “next step” in a defensive investigation; CEH methodology stresses authorized, controlled testing and prioritizes risk reduction over interacting with suspicious external hosts.

Thus, CEH-aligned best practice is immediate isolation and firmware-level investigation.