ISA-IEC-62443 Exam Dumps - ISA Cybersecurity Questions and Answers

 Modbus over Ethernet, also known as Modbus/TCP, is a protocol that encapsulates the Modbus/RTU data string inside the data section of the TCP frame. It then sets up a client/server exchange between nodes, using TCP/IP addressing to establish connections1. This makes it easy to manage in a firewall, because the firewall can filter the traffic based on the source and destination IP addresses and the TCP port number. The default TCP port for Modbus/TCP is 502, but it can be changed if needed. Modbus/TCP does not use any other ports or protocols, so the firewall rules can be simple and specific. References:

8: Open Modbus/TCP Specification, RTA Automation, 2010.

[9]: Modbus Application Protocol Specification V1.1b3, Modbus Organization, 2012.

In the Assess phase of the IACS Cybersecurity Lifecycle (as defined in ISA/IEC 62443-2-1 and 62443-3-2), the main objective is to identify assets, analyze risks, and assign a Target Security Level (SL-T) for each zone or conduit. This sets the foundation for design and implementation decisions. Achieving or verifying the SL-A (Achieved Security Level) occurs later in the lifecycle, after implementation.

The “Maintain” phase is the fourth phase of the IACS Cybersecurity Lifecycle described in ISA/IEC 62443-2-1. A key activity in this phase is managing changes (also known as “change management”). This activity ensures that any modifications to the IACS environment (hardware, software, processes, etc.) are evaluated for cybersecurity impact, and proper controls are implemented to maintain the intended security posture. While risk assessment is typically done in the Assess phase, and allocating assets and designing countermeasures belong to earlier phases, managing changes is essential for ensuring ongoing compliance and effectiveness of cybersecurity controls over time.

The reference model described in ISA/IEC 62443-1-1 (see Figure 2) starts at a high level and encompasses all levels of the ISA-95 model (Levels 0 to 4), which range from field devices up to business logistics systems. This model provides a holistic, layered view of all the equipment, systems, and information flows in industrial automation.

ISA/IEC 62443 defines Security Levels (SL 0–4) based on attacker capability, motivation, and resources.

Step 1: Understanding SL 4

SL 4 is defined as protection against intentional violations using sophisticated means with extended resources. This includes highly motivated attackers, potentially well-funded and highly skilled.

Step 2: Why SL 4 applies

The question explicitly mentions:

High motivation

Extended resources

Sophisticated means

This description exactly matches the formal definition of SL 4 in ISA/IEC 62443-3-3 and 4-2.

Step 3: Why lower SLs are insufficient

SL 1–3 do not assume extended resources or the highest attacker sophistication.

Thus, SL 4 is the correct target.

ISA/IEC 62443 places primary accountability for cybersecurity risk on the asset owner, particularly during the Operation and Maintenance phase of the IACS lifecycle. This phase is where systems run for years or decades, and cybersecurity effectiveness depends less on design intent and more on how people and processes operate daily.

Step 1: Lifecycle responsibility of the asset owner

ISA/IEC 62443-2-1 requires the asset owner to establish, operate, and maintain an IACS Security Program. During operation, cybersecurity controls must be embedded into routine organizational activities such as operations, maintenance, incident handling, training, and change management.

Step 2: Integration with people and processes

The standard explicitly recognizes that technology alone cannot manage cybersecurity risk. Operators, engineers, maintenance staff, and managers must understand their cybersecurity roles. Embedding IACS security into organizational processes ensures consistent execution across shifts, teams, and sites.

Step 3: Avoiding incorrect interpretations

Immediate decommissioning is not an operational objective. Allowing unrestricted remote updates by suppliers contradicts governance requirements. Granting full control to maintenance providers violates the asset owner’s accountability.

Step 4: Operational resilience

By embedding IACS security into organizational culture and workflows, the asset owner ensures that security measures are sustained, monitored, and improved over time.

Therefore, the correct reason is to embed the IACS within organizational processes and people.

The formula for risk in ISA/IEC 62443 is typically expressed as:

Risk = Threat × Vulnerability × Consequence

This means that risk is a product of the likelihood that a threat will exploit a vulnerability and the impact (consequence) if that event occurs. This formula is consistently used in both the general information security domain and explicitly referenced in the ISA/IEC 62443-3-2 standard in the context of IACS risk assessments.

ISA/IEC 62443 distinguishes between voluntary standards and legally binding obligations. Understanding this distinction is essential for compliance planning.

Step 1: Definition of regulations

Regulations are rules issued by governments or authorized regulators that carry legal force. Non-compliance can result in penalties, fines, or legal action.

Step 2: Standards vs regulations

ISA/IEC 62443 itself is a voluntary international standard unless incorporated into law or contracts. Frameworks and special publications provide guidance but lack inherent legal enforceability.

Step 3: ISA/IEC 62443 context

The standard acknowledges that asset owners must comply with applicable regulations first, then apply standards like 62443 to meet cybersecurity objectives.

Step 4: Correct terminology

Only regulations meet the definition of legally enforceable rules.

Therefore, the correct answer is Regulations.

The ISA/IEC 62443 series is structured into logical groups to address different aspects of industrial cybersecurity. Historically, the series was organized into Parts 1 through 4, covering general concepts, management system requirements, system requirements, and component requirements. As the standard evolved, the need arose to address sector-specific and application-specific cybersecurity needs without modifying the core requirements.

To address this, ISA introduced the concept of cybersecurity profiles. These profiles allow industries (such as oil and gas, power, water, or manufacturing) to select and tailor existing ISA/IEC 62443 requirements for their specific operational context while preserving consistency with the base standard.

The Profiles Group is formally designated as ISA/IEC 62443-5-x. This numbering clearly distinguishes profiles from foundational requirements and ensures that:

No new security requirements are created

Existing requirements are selected, scoped, and referenced appropriately

Alignment with Parts 2, 3, and 4 is preserved

By allocating profiles to the 5-x series, ISA ensures modularity and prevents fragmentation of the standard. Profiles serve as an application layer over existing requirements, enabling consistent adoption across sectors without redefining core security controls.

Parts 3-x and 4-x remain dedicated to system and component requirements, while 6-x does not exist in the published structure for profiles. Therefore, 5-x is the correct and formally defined answer.

ISA/IEC 62443 recommends using a firewall to segment and protect the plant floor (Operational Technology or OT network) from the rest of the company’s Information Technology (IT) networks. Firewalls enforce security policies by controlling and monitoring traffic, helping to prevent unauthorized access and potential threats from traversing between business and control networks. Hubs and switches do not provide security; routers may offer some basic filtering, but firewalls are explicitly designed for this purpose.