A water treatment facility uses a legacy SCADA system that relies on Modbus TCP to communicate between the HMI and PLCs. The facility recently connected the SCADA network to the corporate IT network for reporting, but the security team is concerned about the lack of authentication and encryption in Modbus. They need to reduce the risk of an attacker sending malicious commands to the PLCs. Which control is the most effective immediate mitigation?

Replace all PLCs with newer models that support OPC UA

Implement network segmentation with a firewall that restricts Modbus traffic to only the HMI and PLCs

Enable encryption on the existing Modbus TCP traffic using a VPN tunnel

Install antivirus software on the PLCs

EC-CouncilCertified Cybersecurity Technician

Domain 4Objective 4

IoT and OT Security CCT Practice Questions (Page 11)

Part of the Cloud, Wireless, Mobile, and IoT/OT Security domain, which makes up ~17% of our current practice bank.

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A water treatment facility uses a legacy SCADA system that relies on Modbus TCP to communicate between the HMI and PLCs. The facility recently connected the SCADA network to the corporate IT network for reporting, but the security team is concerned about the lack of authentication and encryption in Modbus. They need to reduce the risk of an attacker sending malicious commands to the PLCs. Which control is the most effective immediate mitigation?
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IoT and OT Security CCT Practice Questions (Page 11)

Questions 51–51

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