CyberCertPrepOT Security FundamentalsOT Fundamentals: Safety Systems & Physical SecurityMEDIUMFree question
An integrator proposes letting the BPCS write setpoints into the SIS over Modbus TCP for operator convenience. What is the strongest objection?
- A.Modbus TCP lacks any register type that holds analog values
- B.A BPCS compromise could then alter safety trip settings
- C.The SIS logic solver would need a separate IP subnet mask
- D.Write commands raise the SIS scan time above one second
Why B is correct
Writable links from the BPCS into the SIS let an attacker or a faulty control program change trip setpoints or bypass flags, which defeats the independence the SIS exists to provide. Modbus holding registers carry analog values fine and scan time is not the issue.
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