ISA/IEC 62443 Cybersecurity Fundamentals Specialist — Question 35

Which is the PRIMARY reason why Modbus over Ethernet is easy to manage in a firewall?

Answer options

• A. Modbus uses a single master to communicate with multiple slaves using simple commands.
• B. Modbus is a proprietary protocol that is widely supported by vendors.
• C. Modbus uses explicit source and destination IP addresses and a single known TCP port.
• D. Modbus has no known security vulnerabilities, so firewall rules are simple to implement.

Correct answer: C

Explanation

The correct answer is C because Modbus uses explicit source and destination IP addresses along with a single TCP port, making it easier for firewalls to manage and filter traffic. Option A describes the communication model but does not address firewall management. Option B mentions vendor support, which is not related to firewall management, and option D incorrectly asserts that Modbus has no security vulnerabilities, which complicates firewall rule implementation.