ISA99 ICSSCADA Practice Questions (Page 2)

Questions 6–10

1. 6expert · hard

   A hospital is implementing ISA99 for its building automation system (BAS) that controls HVAC and access control. The BAS is connected to the IT network for monitoring. The security team wants to create zones and conduits. The BAS has a mix of legacy devices that do not support authentication and modern devices that do. The risk assessment assigns a target security level of SL 2 to the BAS zone. The team is considering two designs: (A) put all BAS devices in one zone and implement a firewall to the IT network, or (B) split the BAS into two zones: one for legacy devices with stricter access controls and one for modern devices. Which design is more appropriate?

   • ADesign A because it is simpler and the firewall to IT is the main security boundary.
   • BDesign B because legacy devices should always be in a separate zone, regardless of security requirements.
   • CDesign A because all devices must be in the same zone to communicate with each other.
   • DDesign B because it allows the legacy zone to have compensating controls and the modern zone to achieve SL 2 more easily.
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2. 7application · medium

   A pharmaceutical company is implementing ISA99 security levels for its manufacturing execution system (MES). The MES is in a zone that also contains the historian and the domain controller. The risk assessment has determined that the zone requires SL 2. The current system has no authentication on the MES, and the network is shared with the IT office network. What is the most appropriate action to achieve SL 2?

   • AImplement strong authentication for all users and segment the MES zone from the IT network with a firewall.
   • BUpgrade the MES to the latest version and apply all patches, but keep the network as is.
   • CDisconnect the MES from the network entirely to eliminate the risk.
   • DDocument that the current state meets SL 2 because the MES is not directly connected to the internet.
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4. 8application · medium

   A water utility is conducting an ISA99 risk assessment for its SCADA system. The assessment team has identified a vulnerability in the human-machine interface (HMI) software that could allow an attacker to alter setpoints. The team is now selecting countermeasures. According to ISA99, what should the team do next?

   • AEvaluate the risk reduction of each potential countermeasure and select the one that brings the residual risk to an acceptable level.
   • BIncrease the security level of the HMI zone to SL 4 to mitigate the vulnerability.
   • CImmediately apply the vendor's patch to the HMI software, regardless of the operational impact.
   • DDocument the vulnerability and accept the risk because the HMI is not directly connected to the internet.
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5. 9application · medium

   A control systems engineer is explaining ISA99 to a colleague. They state that ISA99 is a series of standards. Which statement best describes the relationship between ISA99 and ISA-62443?

   • AISA99 is a certification program, and ISA-62443 is the corresponding exam.
   • BISA99 is the committee that develops the ISA-62443 series of standards.
   • CISA99 and ISA-62443 are two independent standards with no relationship.
   • DISA-62443 is a single standard that replaces ISA99.
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6. 10expert · hard

   A company is implementing ISA99 guidance for a new facility. The facility has a control network and a business network. The control network contains a PLC that controls a critical process. The business network contains the ERP system. The company wants to allow the ERP system to receive production data from the PLC, but not to send commands to the PLC. What is the most appropriate ISA99 implementation guidance?

   • AUse a firewall with a rule that allows the ERP to send data to the PLC, but blocks the PLC from sending data to the ERP.
   • BPlace the PLC and ERP in the same zone because they need to communicate.
   • CCreate separate zones for the PLC and ERP, and use a data diode to allow one-way communication from the PLC to the ERP.
   • DConfigure the ERP to only read data from the PLC using a read-only database connection.
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