ISA99 ICSSCADA Practice Questions (Page 5)

Questions 21–25

1. 21foundation · easy

   Which of the following is an example of the practical guidance provided by ISA99 for implementing security in industrial environments?

   • ARequiring the use of a specific antivirus software on all workstations
   • BRecommending the use of network segmentation to limit the spread of malware
   • CMandating that all control systems be disconnected from the internet
   • DSpecifying the exact password length and complexity for all users
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2. 22application · medium

   A manufacturing company is conducting an ISA99 risk assessment for its packaging line. The team identifies a vulnerability in the legacy HMI that cannot be patched. They are considering several mitigation options. Which approach best aligns with ISA99's risk assessment methodology?

   • AAccept the risk because the HMI is legacy and the vulnerability is known but not exploitable.
   • BReplace the HMI immediately with a new model, regardless of cost, to eliminate the vulnerability.
   • CIncrease the target security level to SL 4 to force a higher level of protection.
   • DImplement a compensating control, such as network segmentation or application whitelisting, to reduce the likelihood of exploitation.
   Reveal Solution Discussion Select an answer first
4. 23application · medium

   A chemical plant is upgrading its batch control system. The safety engineering team has determined that a cyber incident causing a loss of view or control could lead to a serious environmental release. The plant's risk assessment identifies a target security level of SL 3 for the control network. The network architect proposes placing all control devices in a single flat network with no segmentation. What is the most appropriate response?

   • AAccept the flat network because SL 3 only applies to the safety instrumented system, not the control network.
   • BApply SL 3 countermeasures only to the HMI workstations, since they are the primary entry point for attackers.
   • CImplement zones and conduits to segment the control network and enforce SL 3 requirements at the zone boundaries.
   • DReduce the target SL to SL 1 to avoid the cost of segmentation, since the plant has never experienced a cyber incident.
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5. 24foundation · easy

   What is the primary purpose of dividing an industrial network into zones as per ISA99?

   • ATo reduce the number of IP addresses required for the network
   • BTo increase network speed by reducing broadcast domains
   • CTo isolate all industrial devices from each other to prevent any communication
   • DTo group assets with similar security requirements and apply consistent security policies
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6. 25expert · medium

   A manufacturing company is implementing ISA99 foundational requirements for its production line. The production line has a robotic arm that is controlled by a PLC. The PLC is connected to a safety PLC that monitors the robotic arm's emergency stop. The company wants to ensure that the safety PLC cannot be accessed by the production PLC. Which ISA99 foundational requirement is most directly applied by implementing a firewall between the production PLC and the safety PLC?

   • AUse control (UC)
   • BData integrity (DI)
   • CRestricted data flow (RDF)
   • DAccess control (AC)
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