PERA Level 0 & 1 Technology Overview and Compromise GICSP Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A natural gas compressor station uses an RTU to monitor suction and discharge pressures. The RTU communicates with a SCADA master via a satellite link. The satellite link has high latency. Which of the following is the MOST appropriate way to handle the latency in the control logic?

   • AMove all control logic to the SCADA master to ensure consistent decisions.
   • BUse a faster protocol such as Modbus TCP instead of the satellite link.
   • CIncrease the polling frequency to reduce the impact of latency.
   • DImplement local control logic in the RTU to maintain safe operation if communication is lost.
   Reveal Solution Discussion Select an answer first
2. 12application · medium

   A manufacturing plant has a conveyor belt with a proximity sensor that detects product jams. The sensor is wired to a PLC input. The PLC is programmed to stop the belt when the sensor is activated. An attacker has gained access to the PLC's programming port. Which of the following is the MOST direct way the attacker could cause the belt to continue running during a jam?

   • ASend a false 'clear' signal to the PLC from the HMI.
   • BIncrease the sensor's sensitivity so it does not detect the jam.
   • CModify the PLC program to ignore the sensor input.
   • DPhysically disconnect the sensor from the PLC input.
   Reveal Solution Discussion Select an answer first
4. 13application · medium

   A wastewater treatment plant has a PLC that controls aeration blowers. The PLC reads a dissolved oxygen (DO) sensor (4-20 mA) and adjusts the blower speed via a variable frequency drive (VFD) using a 4-20 mA signal. The DO sensor is located in a basin that is subject to fouling. The plant has noticed that the DO readings are drifting over time. Which of the following is the most likely cause?

   • AThe PLC's analog input module is not calibrated, causing incorrect readings.
   • BThe VFD is not receiving the correct 4-20 mA signal from the PLC.
   • CThe DO sensor is not calibrated regularly, causing drift.
   • DThe DO sensor's membrane is fouled, reducing the sensor's response.
   Reveal Solution Discussion Select an answer first
5. 14expert · medium

   A power utility has a legacy RTU that communicates with a DCS via a serial protocol. The RTU has no authentication. An attacker has gained access to the serial link. Which of the following attacks would have the MOST severe impact on the physical process?

   • ASend a continuous stream of 'open breaker' commands to the RTU.
   • BReplay a previously captured 'open breaker' command to the RTU.
   • CModify the RTU's configuration to change the scaling of analog inputs.
   • DInject a false 'breaker closed' status message to the DCS.
   Reveal Solution Discussion Select an answer first
6. 15foundation · easy

   Which of the following is a primary purpose of the Purdue Enterprise Reference Architecture (PERA) model in industrial control systems?

   • ATo replace the need for network firewalls by providing inherent security at each level.
   • BTo define the physical layout of equipment on the plant floor.
   • CTo specify the exact brand and model of PLCs that must be used in a plant.
   • DTo define a hierarchical framework for separating and organizing ICS functions from the physical process up to enterprise systems.
   Reveal Solution Discussion Select an answer first