ISA-IEC-62443 ISA/IEC 62443 Cybersecurity Fundamentals Specialist Question and Answers

In the ISA/IEC 62443 framework, Security Levels (SLs) are categorized into three distinct types:

Target SL (SL-T) – The security level required based on risk assessment

Capability SL (SL-C) – The level a component or system can support

Achieved SL (SL-A) – The level actually implemented in the system

“Three types of security levels are defined:

Target (SL-T): derived from risk analysis

Capability (SL-C): supported by the product or system

Achieved (SL-A): implemented and operational in the environment”

— ISA/IEC 62443-1-1:2007, Clause 3.2.4 and Table 3

This classification supports gap analysis and helps asset owners ensure their system meets both required and feasible security levels.

The ISA/IEC 62443 standards series was originally developed by the International Society of Automation (ISA) and then adopted and published by the International Electrotechnical Commission (IEC) as the IEC 62443 series. The IEC is the primary international body responsible for the ongoing development, maintenance, and publication of these standards, which are recognized globally for IACS cybersecurity. ANSI is a US standards body, NIST is responsible for US federal cybersecurity frameworks, and ETSI develops telecommunications standards for Europe, but IEC is the correct answer here.

In ISA/IEC 62443-2-1, the Cyber Security Management System (CSMS) includes multiple categories. One of these is “Addressing Risk”, which is composed of 4 element groups, as outlined in Figure 3 – CSMS Elements of the standard.

The 4 element groups under "Addressing Risk" are:

Risk analysis and management

Security policy, organization, and awareness

Selected security countermeasures

Personnel security

“The Addressing Risk category of the CSMS consists of four element groups: risk analysis and management, security policy and awareness, selected countermeasures, and personnel security.”

— ISA/IEC 62443-2-1:2010, Figure 3 and Clause 4.2.2

The NIS2 Directive, an update to the European Union’s cybersecurity directive, introduces several new requirements, including the establishment of a cyber crisis management framework at both national and EU levels. This is designed to coordinate effective responses to major cybersecurity incidents and crises. NIS2 goes beyond mandating compliance or focusing only on physical security and emphasizes collaboration between the public and private sectors.

OPC Classic uses Microsoft's DCOM (Distributed Component Object Model) for communication, which dynamically opens multiple ports, making it extremely difficult to manage with firewalls.

“OPC Classic is firewall-unfriendly because DCOM requires dynamic port negotiation, making it difficult to define consistent firewall rules.”

— ISA/IEC 62443-3-3:2013, Annex A – Communication Protocols and Security Concerns

This lack of port predictability presents a significant security and operational risk, which led to the development of OPC UA, which uses fixed ports and supports encryption.

According to the ISA/IEC 62443 standards, the level of risk an organization is willing to tolerate is determined by the management, as they are responsible for defining the business and risk objectives, as well as the security policies and procedures for the organization. The management also has the authority to allocate the necessary resources and assign the roles and responsibilities for implementing and maintaining the security program. The legal, operations, and safety departments may provide input and feedback to the management, but they do not have the final say in determining the risk tolerance level. References: ISA/IEC 62443-2-1:2010 - Establishing an industrial automation and control systems security program, section 4.2.1.

ISA/IEC 62443-1-3 is specifically titled "System Security Conformance Metrics" and introduces a methodology to develop quantitative metrics for assessing how well a system conforms to the ISA/IEC 62443 requirements.

“Part 1-3 defines a set of metrics to quantitatively measure the conformance of systems and components to the ISA/IEC 62443 series. It supports repeatable assessment and benchmarking.”

— ISA/IEC 62443-1-3:2013, Scope and Clause 5

This allows organizations to establish measurable KPIs and drive continuous improvement in IACS cybersecurity programs.

The application layer is the topmost layer of the OSI model, which provides the interface between the user and the network. It includes protocols specific to network applications such as email, file transfer, and reading data registers in a PLC. These protocols deliver and format information, possibly with encryption and security, to ensure reliable and meaningful communication between different applications. The application layer does not include user applications, which are separate from the network protocols. The application layer also does not provide the mechanism for opening, closing, and managing a session between end-user application processes, which is the function of the session layer. References:

ISA/IEC 62443 Cybersecurity Fundamentals Specialist Study Guide, page 181

Using the ISA/IEC 62443 Standards to Secure Your Control System, page 82

The application layer in network protocols, such as in the OSI model or the TCP/IP protocol suite, is primarily responsible for providing services directly to user applications. This layer is involved in:

Option A: Including protocols specific to network applications such as email, file transfer, and industrial protocols like reading data registers in a Programmable Logic Controller (PLC). This is a core function of the application layer as it facilitates specific high-level networking capabilities.

Option D: Delivering and formatting information, which can include encryption and ensuring the security of data as it is transmitted across the network. This includes protocols like HTTP for web browsing which can encrypt data via HTTPS, SMTP for secure email transmission, and FTP for secure file transfer.

ISA/IEC 62443-2-1 explicitly requires that the IACS Security Program be integrated into the organization’s overall management structure.

Step 1: Integration principle

The standard states that IACS security must align with business processes, governance, and enterprise security management rather than operate in isolation.

Step 2: Alignment with ISMS

Where an Information Security Management System (ISMS) exists, the IACS SP should be embedded within it to ensure consistent risk management, policy enforcement, and continuous improvement.

Step 3: Why other options are incorrect

Standalone security programs create silos. Full outsourcing violates asset owner accountability. Purely technical approaches ignore human and process factors.

Step 4: Operational outcome

Embedding the SP ensures sustainability, consistency, and executive oversight.

Therefore, the correct answer is by embedding it into organizational processes and the ISMS.

API 1164 is an industry sector-specific standard that provides guidance on the cybersecurity of pipeline supervisory control and data acquisition (SCADA) systems. API stands for American Petroleum Institute, which is the largest U.S. trade association for the oil and natural gas industry. API 1164 was first published in 2004 and revised in 2009 and 2021. The latest version of the standard aligns with the ISA/IEC 62443 series of standards and incorporates the concepts of security levels, zones, and conduits. API 1164 covers the security lifecycle of pipeline SCADA systems, from risk assessment and policy development to implementation and maintenance. The standard also defines roles and responsibilities, security requirements, security controls, and security assessment methods for pipeline SCADA systems.

Datagram Transport Layer Security (DTLS) and Secure Sockets Layer (SSL) are both commonly used protocols for managing secure data transmission on the Internet. DTLS is a variant of SSL that is designed to work over datagram protocols such as UDP, which are used for real-time applications such as voice and video. SSL is a protocol that provides encryption, authentication, and integrity for data transmitted over TCP, which is used for reliable and ordered delivery of data. Both DTLS and SSL use certificates and asymmetric cryptography to establish a secure session between the communicating parties, and then use symmetric cryptography to encrypt the data exchanged. DTLS and SSL are widely used in web browsers, email clients, VPNs, and other applications that require secure communication over the Internet. References:

ISA/IEC 62443 Standards to Secure Your Industrial Control System, Module 3: Introduction to Cryptography, pages 3-5 to 3-7

Using the ISA/IEC 62443 Standards to Secure Your Control System, Chapter 6: Securing Communications, pages 125-126

In the context of international standards and frameworks, SDO stands for “Standards Development Organization.” SDOs are organizations like ISA, IEC, ISO, and NIST, which are responsible for developing, maintaining, and publishing standards used globally for industrial cybersecurity and other domains.

The ISASecure Integrated Threat Analysis (ITA) Program is a certification scheme that certifies off-the-shelf automation and control systems to the ISA/IEC 62443 series of standards1. The ITA Program consists of three main components2:

Software Development Security Assurance (SDSA): This component evaluates the security lifecycle and practices of the product supplier, such as security requirements, design, implementation, verification, and maintenance. The SDSA certification is based on the ISA/IEC 62443-4-1 standard.

Functional Security Assessment (FSA): This component verifies the security functions and features implemented in the product, such as identification and authentication, access control, encryption, audit logging, and security management. The FSA certification is based on the ISA/IEC 62443-4-2 standard.

Communications Robustness Testing (CRT): This component tests the resilience of the product against network attacks, such as denial-of-service, fuzzing, spoofing, and replay. The CRT certification is based on the ISA/IEC 62443-4-2 and ISA/IEC 62443-3-3 standards .

A significant challenge with firewalls in industrial environments is deciding how they should be configured. The complexity arises from needing to balance operational requirements (such as process data flow) with security needs (such as blocking unauthorized access). Misconfiguration can lead either to security gaps or to unnecessary operational disruptions. Firewalls can filter many types of traffic (not just HTTP) and while updates are important, configuration is the biggest ongoing challenge.

Phishing is a type of cyberattack that relies on a human weakness to succeed. Phishing is the practice of sending fraudulent emails or other messages that appear to come from a legitimate source, such as a bank, a government agency, or a trusted person, in order to trick the recipient into revealing sensitive information, such as passwords, credit card numbers, or personal details, or into clicking on malicious links or attachments that may install malware or ransomware on their devices. Phishing is a common and effective way of compromising the security of industrial automation and control systems (IACS), as it can bypass technical security measures by exploiting the human factor. Phishing can also be used to gain access to the IACS network, to conduct reconnaissance, to launch further attacks, or to cause damage or disruption to the IACS operations. The ISA/IEC 62443 series of standards recognize phishing as a potential threat vector for IACS and provide guidance and best practices on how to prevent, detect, and respond to phishing attacks. Some of the recommended countermeasures include:

Educating and training the IACS staff on how to recognize and avoid phishing emails and messages, and how to report any suspicious or malicious activity.

Implementing and enforcing policies and procedures for email and message security, such as using strong passwords, verifying the sender’s identity, and not opening or clicking on unknown or unsolicited links or attachments.

Applying technical security controls, such as antivirus software, firewalls, spam filters, encryption, and authentication, to protect the IACS devices and network from phishing attacks.

Monitoring and auditing the IACS network and devices for any signs of phishing attacks, such as anomalous or unauthorized traffic, connections, or activities, and taking appropriate actions to contain and mitigate the impact of any incidents. References:

ISA/IEC 62443-1-1:2009, Security for industrial automation and control systems - Part 1-1: Terminology, concepts and models1

ISA/IEC 62443-2-1:2009, Security for industrial automation and control systems - Part 2-1: Establishing an industrial automation and control systems security program2

ISA/IEC 62443-2-4:2015, Security for industrial automation and control systems - Part 2-4: Security program requirements for IACS service providers3

ISA/IEC 62443-3-3:2013, Security for industrial automation and control systems - Part 3-3: System security requirements and security levels4

ISA/IEC 62443-4-2:2019, Security for industrial automation and control systems - Part 4-2: Technical security requirements for IACS components5

According to ISA/IEC 62443-3-2, the risk analysis phase in the IACS security lifecycle includes both the business rationale and the risk identification and classification. This ensures that risk decisions are based not only on technical vulnerability but also on business impact and operational context.

“The risk analysis process includes identification and classification of risks based on a defined business rationale. This ensures that the protection requirements are aligned with the organization’s risk tolerance and operational priorities.”

— ISA/IEC 62443-3-2:2020, Section 6.4 – Risk Assessment and SL Targeting

The term business rationale refers to understanding the value and criticality of the asset or system in order to make informed security decisions.

In the OSI model, the Data Link layer (Layer 2) is responsible for error detection/correction and for assigning and handling MAC (Media Access Control) addresses, which are unique identifiers for network interfaces. This layer ensures reliable transmission of data frames between devices on the same local network. The Network layer (Layer 3) handles IP addressing and routing, not MAC addresses.

According to the ISA/IEC 62443-3-2 standard, a security zone is a grouping of systems and components based on their functional, logical, and physical relationship that share common security requirements. The primary objective of defining a security zone is to apply a consistent level of protection to the assets within the zone, based on their criticality and risk assessment. A security zone may contain assets from different vendors, different levels in the Purdue model, or different physical locations, as long as they have the same security requirements. A security zone may also be subdivided into subzones, if there are different security requirements within the zone. A conduit is a logical or physical grouping of communication channels connecting two or more zones that share common security requirements.

 OPC Classic uses DCOM, which dynamically assigns any port between 1024 and 65535. Comprehensive Explanation: OPC Classic is a software interface technology that uses the Distributed Component Object Model (DCOM) protocol to facilitate the transfer of data between different industrial control systems. DCOM is a Microsoft technology that allows applications to communicate across a network. However, DCOM is not designed with security in mind, and it poses several challenges for firewall configuration. One of the main challenges is that DCOM does not use fixed TCP port numbers, but rather negotiates new port numbers within the first open connection. This means that intermediary firewalls can only be used with wide-open rules, leaving a large range of ports open for potential attacks. This makes OPC Classic very “firewall unfriendly” and reduces the security and protection they provide. References:

Tofino Security OPC Foundation White Paper

Step 2 (for client or server): Configuring firewall settings - GE

Secure firewall for OPC Classic - Design World

A Local Area Network (LAN) is not a strategy for deploying a Wide Area Network (WAN). WAN deployment strategies include using the public Internet, private enterprise WANs, or carrier-managed WANs. LANs, by definition, serve local, not wide-area, connectivity. ISA/IEC 62443 standards refer to different strategies for extending network communications over broader geographic regions, but do not classify LAN as a WAN deployment option.

Asymmetric (public) key algorithms are a type of cryptographic algorithms that require more than one key. Asymmetric key algorithms use a pair of keys, one for encryption and one for decryption, that are mathematically related but not identical1. The encryption key is usually made public, while the decryption key is kept private. This allows anyone to encrypt a message using the public key, but only the intended recipient can decrypt it using the private key1. Asymmetric key algorithms are also known as public key algorithms or public key cryptography1. Asymmetric key algorithms are used for various purposes, such as digital signatures, key exchange, and encryption2. Some examples of asymmetric key algorithms are RSA, Diffie-Hellman, ElGamal, and Elliptic Curve Cryptography2.

ISA/IEC 62443-3-2 provides explicit guidance on performing security risk assessments that directly inform system architecture, including the design of zones and conduits.

Step 1: Purpose of Part 3-2

This part defines how to identify threats, vulnerabilities, and consequences, and how to derive Target Security Levels (SL-T).

Step 2: Zones and conduits linkage

The standard requires that zones be defined based on risk and criticality, and conduits be established to control communications between zones. This architectural outcome is a direct result of the 3-2 risk assessment process.

Step 3: Integrator relevance

System integrators use Part 3-2 to translate risk results into concrete network segmentation and security boundaries.

Step 4: Why other parts do not apply

Other parts address governance, metrics, or product development, not architectural risk-driven design.

The selection of countermeasures is driven by the output from a risk assessment, which identifies the risks and their associated likelihood and consequences for each zone and conduit in the industrial automation and control system (IACS). The risk assessment also determines the target security level (SL-T) for each zone and conduit, which represents the desired level of protection against the identified threats. The countermeasures are then selected based on the SL-T and the existing security level (SL-A) of the zone and conduit, as well as the cost and feasibility of implementation. The countermeasures should aim to reduce the risk to an acceptable level by increasing the SL-A to meet or exceed the SL-T. References: ISA/IEC 62443-3-2:2018 - Security risk assessment for system design, ISA/IEC 62443-3-3:2013 - System security requirements and security levels, ISA/IEC 62443 Cybersecurity Fundamentals Specialist Training Course

ISA/IEC 62443 is officially listed as an Informative Reference in the NIST Cybersecurity Framework (CSF). Informative References provide detailed guidance to help organizations implement the CSF's functions, categories, and subcategories.

“ISA/IEC 62443 is included in the NIST CSF Informative References to help apply risk-based cybersecurity practices to industrial control systems.”

— NIST CSF Informative Reference Catalog, Section: PR.IP and ID.RA

ISA/IEC 62443 aligns well with CSF categories such as Protect (PR) and Identify (ID), especially for operational technology environments.

According to the ISA/IEC 62443 standard, the connections between security zones are called conduits. A conduit is defined as a logical or physical grouping of communication channels connecting two or more zones that share common security requirements. A conduit can be used to control and monitor the data flow between zones, and to apply security measures such as encryption, authentication, filtering, or logging. A conduit can also be used to isolate zones from each other in case of a security breach or incident. A conduit can be implemented using various technologies, such as firewalls, routers, switches, cables, or wireless links. However, these technologies are not synonymous with conduits, as they are only components of a conduit. A firewall, for example, can be used to create multiple conduits between different zones, or to protect a single zone from external threats. Therefore, the other options (firewalls, tunnels, and pathways) are not correct names for the connections between security zones. References:

ISA/IEC 62443-3-2:2016 - Security for industrial automation and control systems - Part 3-2: Security risk assessment and system design1

ISA/IEC 62443-3-3:2013 - Security for industrial automation and control systems - Part 3-3: System security requirements and security levels2

Zones and Conduits | Tofino Industrial Security Solution3

Key Concepts of ISA/IEC 62443: Zones & Security Levels | Dragos4

IT systems and IACS have different security priorities, requirements, and challenges. According to the ISA/IEC 62443 standards, the security priority for IT systems is confidentiality, which means protecting the data from unauthorized access or disclosure. The security priority for IACS is integrity, which means ensuring the accuracy and consistency of the data and the functionality of the system. A loss of integrity in an IACS can have severe consequences, such as physical damage, environmental harm, or human injury. Therefore, IACS cybersecurity must address safety issues, which are not typically considered in IT security. Safety is the ability of the system to prevent or mitigate hazardous events that can cause harm to people, property, or the environment. The ISA/IEC 62443 standards provide guidance and best practices for ensuring the safety and security of IACS, as well as the availability and reliability of the system. Availability is the ability of the system to perform its intended function when required, and reliability is the ability of the system to perform its intended function without failure. These properties are also important for IT systems, but they may have different trade-offs and implications for IACS. For example, an IACS may have stricter performance and availability requirements than an IT system, as a delay or disruption in the IACS operation can affect the industrial process and its outcomes. Additionally, an IACS may have longer equipment lifetimes and less frequent maintenance windows than an IT system, which can make patching and updating more difficult and risky. Furthermore, an IACS may use different technologies and architectures than an IT system, such as legacy devices, proprietary protocols, or specialized hardware. These factors can create compatibility and interoperability issues, as well as increase the attack surface and complexity of the IACS. Therefore, IT security solutions and practices may not be sufficient or suitable for IACS, and they may need to be adapted or supplemented by IACS-specific security measures. The ISA/IEC 62443 standards address these differences and provide a comprehensive framework for securing IACS throughout their lifecycle.

ISA/IEC 62443 clearly distinguishes roles to assign cybersecurity responsibilities across the IACS lifecycle. A company that designs and manufactures embedded devices and network components—such as PLCs, RTUs, switches, or control software—but does not install or operate them is classified as a Product Supplier.

Step 1: Definition of a Product Supplier

Within ISA/IEC 62443 (notably Parts 4-1 and 4-2), a product supplier is the entity responsible for developing and delivering IACS products. Their responsibilities include secure product development, vulnerability handling, patch creation, and providing security-related product documentation.

Step 2: Exclusion of operational roles

Because the company does not perform on-site installation, commissioning, operation, or maintenance, it does not qualify as an integration or maintenance service provider. It also does not own or operate the system, so it is not an asset owner.

Step 3: Security responsibility alignment

ISA/IEC 62443-4-1 assigns product suppliers responsibility for secure development lifecycle practices, while 4-2 defines the technical security capabilities the products must support.

Therefore, the correct role is Product supplier.

 Periodic audits are an essential part of the ISA/IEC 62443 cybersecurity standards, as they help to verify the effectiveness and compliance of the security program. According to the ISA/IEC 62443-2-1 standard, periodic audits should be conducted to evaluate the following aspects1:

The security policies and procedures are consistent with the security requirements and objectives of the organization

The security policies and procedures are implemented and enforced in accordance with the security program

The security policies and procedures are reviewed and updated regularly to reflect changes in the threat landscape, the IACS environment, and the business needs

The security performance indicators and metrics are measured and reported to the relevant stakeholders

The security incidents and vulnerabilities are identified, analyzed, and resolved in a timely manner

The security awareness and training programs are effective and aligned with the security roles and responsibilities of the personnel

The security audits and assessments are conducted by qualified and independent auditors

The security audit and assessment results are documented and communicated to the appropriate parties

The security audit and assessment findings and recommendations are addressed and implemented in a prioritized and systematic way Periodic audits are not only a means to meet regulations or adhere to a schedule, but also a way to validate that the security policies and procedures are performing as intended and achieving the desired security outcomes. Periodic audits also help to identify gaps and weaknesses in the security program and provide opportunities for improvement and enhancement. References: Periodic audits are an essential part of the ISA/IEC 62443 cybersecurity standards, as they help to verify the effectiveness and compliance of the security program. According to the ISA/IEC 62443-2-1 standard, periodic audits should be conducted to evaluate the following aspects1:

The security policies and procedures are consistent with the security requirements and objectives of the organization

The security policies and procedures are implemented and enforced in accordance with the security program

The security policies and procedures are reviewed and updated regularly to reflect changes in the threat landscape, the IACS environment, and the business needs

The security performance indicators and metrics are measured and reported to the relevant stakeholders

The security incidents and vulnerabilities are identified, analyzed, and resolved in a timely manner

The security awareness and training programs are effective and aligned with the security roles and responsibilities of the personnel

The security audits and assessments are conducted by qualified and independent auditors

The security audit and assessment results are documented and communicated to the appropriate parties

The security audit and assessment findings and recommendations are addressed and implemented in a prioritized and systematic way Periodic audits are not only a means to meet regulations or adhere to a schedule, but also a way to validate that the security policies and procedures are performing as intended and achieving the desired security outcomes. Periodic audits also help to identify gaps and weaknesses in the security program and provide opportunities for improvement and enhancement. References:

One of the reasons for the increase in attacks on IACS is the availability of information and tools that can be used to exploit vulnerabilities in these systems. The Internet provides a platform for hackers, researchers, and activists to share their knowledge and techniques for compromising IACS. Some examples of such information and tools are:

Stuxnet: A sophisticated malware that targeted the Iranian nuclear program in 2010. It exploited four zero-day vulnerabilities in Windows and Siemens software to infect and manipulate the programmable logic controllers (PLCs) that controlled the centrifuges. Stuxnet was widely analyzed and reported by the media and security experts, and its source code was leaked online1.

Metasploit: A popular penetration testing framework that contains modules for exploiting various IACS components and protocols. For instance, Metasploit includes modules for attacking Modbus, DNP3, OPC, and Siemens S7 devices2.

Shodan: A search engine that allows users to find devices connected to the Internet, such as webcams, routers, printers, and IACS components. Shodan can reveal the location, model, firmware, and configuration of these devices, which can be used by attackers to identify potential targets and vulnerabilities3.

ICS-CERT: A website that provides alerts, advisories, and reports on IACS security issues and incidents. ICS-CERT also publishes vulnerability notes and mitigation recommendations for various IACS products and vendors4. These sources of information and tools can be useful for legitimate purposes, such as security testing, research, and education, but they can also be misused by malicious actors who want to disrupt, damage, or steal from IACS. Therefore, IACS owners and operators should be aware of the threats and risks posed by the Internet and implement appropriate security measures to protect their systems. References:

The increase in attacks on Industrial Automation and Control Systems (IACS) can be attributed to several factors, including: A. Use of proprietary communications protocols: These can pose security risks because they may not have been designed with security in mind and are often not as well-tested against security threats as more standard protocols. C. Knowledge of exploits and tools readily available on the Internet: The availability of information about vulnerabilities and exploits on the internet has made it easier for attackers to target IACS.

The other options, B and D, are incorrect because: B. The move towards commercial off-the-shelf (COTS) systems, protocols, and networks actually increases risk because these systems are more likely to be known and targeted by attackers, compared to proprietary systems which might benefit from security through obscurity. D. There is actually an increase in risk with more personnel with system knowledge because it enlarges the attack surface – each individual with system knowledge can potentially become a vector for an attack, either maliciously or accidentally.

At layer 4 of the OSI model, also known as the transport layer, the application that will handle a packet inside a host is identified by a TCP/UDP port number. A port number is a 16-bit integer that is assigned to a specific application or service that runs on a host. Port numbers are used to multiplex and demultiplex the data streams that are exchanged between hosts and end systems. Multiplexing is the process of combining multiple data streams into one, while demultiplexing is the process of separating one data stream into multiple ones. Port numbers are part of the header of the transport layer protocol data unit (PDU), which is called a segment for TCP and a datagram for UDP. The header contains the source port number and the destination port number, which indicate the applications that are involved in the communication. For example, if a host sends a packet to another host using the HTTP protocol, which runs on port 80 by default, the source port number would be a random number chosen by the sender, and the destination port number would be 80. The receiver would then use the destination port number to demultiplex the packet and deliver it to the HTTP application.

Port numbers are divided into three ranges: well-known ports (0-1023), registered ports (1024-49151), and dynamic or private ports (49152-65535). Well-known ports are reserved for common and standardized applications and services, such as HTTP (80), FTP (21), and SSH (22). Registered ports are assigned by the Internet Assigned Numbers Authority (IANA) to specific applications and services that request them, such as Skype (49175) and Minecraft (25565). Dynamic or private ports are not assigned by any authority and can be used by any application or service that needs them, such as ephemeral ports that are used for temporary connections.

The other options are not valid identifiers for the application that will handle a packet inside a host at layer 4 of the OSI model. A TCP/UDP application ID is not a term that is used in the OSI model or the TCP/IP model. A TCP/UDP host ID is not a term that is used in the OSI model or the TCP/IP model, and it would be more appropriate for layer 3, which is the network layer, where the host is identified by an IP address. A TCP/UDP registry number is not a term that is used in the OSI model or the TCP/IP model, and it would be more appropriate for layer 5, which is the session layer, where the registry number is used to identify a session between two hosts.

According to the ISA/IEC 62443 Cybersecurity Fundamentals, the risk matrix is a tool used to assess the risk of a particular event. The risk matrix is divided into three categories: likelihood, consequence, and risk. The likelihood is the probability that an event will occur, the consequence is the impact that the event will have, and the risk is the combination of the two. In this case, the risk of a medium likelihood event with high consequence is a high risk, as shown by the red cell in the matrix. References:

ISA/IEC 62443 Cybersecurity Fundamentals

[ISA/IEC 62443 Cybersecurity Certificate Program]

[Cybersecurity Library]

[Using the ISA/IEC 62443 Standard to Secure Your Control Systems]

ISA/IEC 62443-3-2 intentionally avoids mandating a single risk assessment methodology. Instead, it defines requirements for the outcome and consistency of the risk assessment process.

Step 1: Methodology flexibility

The standard allows asset owners to use qualitative, quantitative, or hybrid methods based on system complexity, organizational maturity, and available data.

Step 2: Consistency requirement

What ISA/IEC 62443 does require is that the methodology be documented, repeatable, and consistent, particularly in how risks are ranked and compared.

Step 3: Security Level determination

Consistent risk ranking is essential for determining Target Security Levels (SL-T) and for justifying security decisions during audits.

Step 4: Why other options are incorrect

Avoiding standards undermines rigor. Using only qualitative methods may be insufficient. Mixing methodologies can introduce inconsistency and invalidate comparisons.

Therefore, the approach that best aligns with ISA/IEC 62443 is to follow any documented methodology that uses a consistent risk ranking scale.

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.

According to ISA/IEC 62443-2-4, which defines security requirements for IACS service providers, four maturity levels (ML1–ML4) are established as evaluation criteria for measuring the maturity of cybersecurity practices.

These are:

ML1 – Initial

ML2 – Managed

ML3 – Defined

ML4 – Improving

“This standard defines four maturity levels (ML1 through ML4) to assess the extent of cybersecurity process implementation for service providers.”

— ISA/IEC 62443-2-4:2015, Clause 5.1 – Maturity Level Overview

These maturity levels are used to benchmark and certify service provider practices across different domains like patching, access control, and incident response.

Malware incidents are cited in ISA/IEC 62443 documentation and industry case studies as one of the primary causes of cyber-related production losses in process control environments. Such incidents can result in equipment shutdowns, process interruptions, and loss of visibility or control, leading directly to financial and operational impacts. While human error and hardware failure are also causes of downtime, in the context of “cyber-related” incidents, malware is the main contributor.

ISA/IEC TR 62443-1-5 defines the rules for creating cybersecurity profiles. The key principle is preservation of standard integrity.

Step 1: Purpose of profiles

Profiles allow selection and scoping of existing requirements for specific industries or applications.

Step 2: Restriction on modification

The technical report explicitly states that no new security requirements may be added, and existing requirements must not be altered. This ensures interoperability, auditability, and certification consistency.

Step 3: Correct approach

Profiles may select, exclude, or contextualize requirements, but they cannot redefine them.

Therefore, Option C is correct.

ISA/IEC 62443 emphasizes that physical security and cybersecurity are interdependent and must complement each other to provide robust protection for industrial automation and control systems (IACS). Physical security measures (like locks, fences, access cards) protect against unauthorized physical access, while cybersecurity measures protect against digital threats. Both must work together; for example, a cyber attacker might gain physical access to a control cabinet or a physical intruder might exploit weak network security.

One of the most frequent mistakes in cybersecurity management—according to ISA/IEC 62443 guidance—is focusing only on technological solutions and neglecting other critical components such as people, process, and culture. Effective cybersecurity management must include policies, training, incident response, and continual improvement, not just technical controls. This holistic approach is emphasized throughout the standards, particularly in the sections describing CSMS program elements and organizational responsibilities.

 The ISASecure conformance certification program is managed by the Security Compliance Institute (ISCI), a non-profit organization established in 2007 by a group of industry stakeholders, including end users, suppliers, and integrators. ISCI’s mission is to provide a common industry-accepted set of device and process requirements that drive device security, simplifying procurement for asset owners and device assurance for equipment vendors12. References: 1: ISASecure - IEC 62443 Conformance Certification - Official Site 2: Certifications - ISASecure

IACS stands for “Industrial Automation and Control Systems.” The ISA/IEC 62443 series defines IACS as systems used for industrial automation, process control, and related functions. These include systems such as Distributed Control Systems (DCS), SCADA systems, and PLCs. The term encompasses all electronic systems, networks, and equipment used to automate industrial processes.

In ISA/IEC 62443, Target Security Protection Ratings correspond to the concept of Target Security Levels (SL-T).

Step 1: Definition of target ratings

Target ratings describe the desired level of protection that a system or zone must achieve during operation, based on risk assessment.

Step 2: Difference between target and achieved

Target ratings define what is required.

Achieved ratings (SL-A) describe what has actually been implemented and verified.

Step 3: Why Option D is correct

The target rating outlines the intended security outcome that implementation measures must fulfill during operation, not what currently exists.

Step 4: Why other options are incorrect

Actual achieved levels, cost metrics, or implementation measurements are separate concepts.

Therefore, the correct description is that they outline the desired levels of system security requirements to be fulfilled during operation.

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.

The ISA/IEC 62443-3-2 standard specifies that a key output of the risk assessment process is the establishment of Target Security Levels (SL-Ts) for each security zone or conduit. These target levels define the minimum cybersecurity requirements necessary to mitigate identified risks to an acceptable level. Total risk elimination is generally not possible; instead, setting SL-Ts allows for structured, risk-based implementation of security controls.

The OSI model defines 7 layers for standardizing communications in network systems. The Transport Layer is responsible for reliable data transfer between end systems, including flow control, error correction, and segmentation. It sits between the Network Layer and the Session Layer.

The correct OSI model from top to bottom is:

Application

Presentation

Session

Transport ← Missing layer

Network

Data Link

Physical

“The transport layer provides transparent transfer of data between end users, ensuring complete data transfer.”

— ISA/IEC 62443-3-3:2013, Annex A – Communications Stack and Layered Security Concepts

Understanding the OSI model is crucial when designing secure industrial networks, as ISA/IEC 62443 advocates for layered defense ("defense in depth") at all levels.

“Defense in Depth” is a foundational principle in ISA/IEC 62443, defined as:

“The application of multiple security countermeasures in a layered (stepwise) fashion to protect assets.”

(ISA/IEC 62443-1-1, Clause 3.2.65)

The objective is to reduce the probability that a single point of failure or vulnerability can be exploited to compromise the system. Layers may include physical security, network segmentation, authentication, intrusion detection, and endpoint protection.

From ISA/IEC 62443-3-3:

“Defense in depth should be employed to provide redundancy in security mechanisms. Each layer increases the security of the system and mitigates different types of threats.”

Incorrect Options:

A and B – Misinterpret the concept as technical complexity, rather than layered protection.

C – Refers to physical spacing, not a cybersecurity strategy.

 A recommended default rule for IACS firewalls is to block all traffic by default, and then allow only the necessary and authorized traffic based on the security policy and the zone and conduit model. This is also known as the principle of least privilege, which means granting the minimum access required for a legitimate purpose. Blocking all traffic by default provides a higher level of security and reduces the attack surface of the IACS network. The other choices are not recommended default rules for IACS firewalls, as they may expose the IACS network to unnecessary risks. Allowing all traffic by default would defeat the purpose of a firewall, as it would not filter any malicious or unwanted traffic. Allowing IACS devices to access the Internet would expose them to potential cyber threats, such as malware, phishing, or denial-of-service attacks. Allowing traffic directly from the IACS network to the enterprise network would bypass the demilitarized zone (DMZ), which is a buffer zone that isolates the IACS network from the enterprise network and hosts services that need to communicate between them. References:

ISA/IEC 62443 Standards to Secure Your Industrial Control System training course1

ISA/IEC 62443 Cybersecurity Fundamentals Specialist Study Guide2

Using the ISA/IEC 62443 Standard to Secure Your Control Systems3

The four documents classified under the General category of ISA/IEC 62443 are:

Part 1-1: Terminology, concepts, and models

Part 1-2: Master glossary of terms and definitions

Part 1-3: System security conformance metrics

Cybersecurity awareness programs are most effective when tailored to the organization’s audience, are aligned with corporate policies, and are communicated regularly. ISA/IEC 62443-2-1 emphasizes the importance of ongoing cybersecurity training and awareness, customized to different user roles, as a critical factor in reducing human-related security risks.

System availability is a core objective of ISA/IEC 62443, reflected in the Resource Availability (RA) foundational requirement. When frequent shutdowns occur, the standard directs attention to recovery and resilience mechanisms.

Step 1: Role of SP Element 8

SP Element 8 addresses backup, restore, and recovery capabilities. These activities ensure that systems can be restored quickly and reliably following failures, cyber incidents, or operational errors.

Step 2: Availability focus

Unexpected shutdowns often reveal weaknesses in backup integrity, restoration procedures, or recovery testing. ISA/IEC 62443 requires backups to be verified, protected, and periodically tested to ensure operational continuity.

Step 3: Why other SP Elements are secondary

Supply chain security, change control, and logging are important but do not directly restore operations after shutdowns. Backup and recovery directly impact downtime reduction.

Step 4: Operational outcome

Reviewing SP Element 8 activities helps identify gaps in restoration time objectives, backup completeness, and recovery procedures.

Thus, SP Element 8 – Backup restoration is the most relevant.

The second edition (2024) of ISA/IEC 62443-2-1 introduced a significant structural improvement by eliminating duplication of Information Security Management System (ISMS) requirements. The first edition (2010) contained content that overlapped substantially with ISO/IEC 27001-style ISMS controls, leading to redundancy and unnecessary implementation burden.

In the updated edition, ISA clarified that 62443-2-1 is not intended to replace a general-purpose ISMS, but rather to extend and specialize it for Industrial Automation and Control Systems (IACS). As a result, duplicated ISMS clauses were removed or streamlined, and the focus shifted to IACS-specific risks, operational realities, and lifecycle concerns.

This change improves:

Compatibility with existing enterprise ISMS implementations

Clarity of roles between IT security governance and OT security management

Practical adoption by asset owners operating both IT and OT environments

Importantly, supply chain security, lifecycle management, and organizational governance were not removed. Instead, they were better aligned and referenced to avoid redundancy. The PDCA model remains implicit but was not newly introduced in 2024.

Thus, the defining change is the elimination of duplicated ISMS requirements, making Option B correct.

ISA/IEC 62443-6-1 defines a security evaluation methodology specifically intended for use with 62443-2-4 (Service Providers) and 62443-4-1 (Secure Development Lifecycle). It provides assessment techniques and scoring models for verifying conformance.

“This part specifies requirements and provides guidance for the assessment of conformity to selected parts of the ISA/IEC 62443 series. It supports evaluation of suppliers per 62443-2-4 and 62443-4-1.”

— ISA/IEC 62443-6-1:2020, Clause 1 – Scope

It is not focused on patching, technologies, or security phases, but rather on evaluating and validating conformance to the standards.

A Host-based Intrusion Detection System (IDS) is a device or software application used to monitor and analyze the internals of a computing system (host) for malicious activity or policy violations. Unlike routers, switches, or even firewalls, which focus on network traffic or connectivity, a host-based IDS operates on individual machines to detect unauthorized activity or changes.

Modbus, in its traditional form, lacks inherent security features. According to ISA/IEC 62443, one of the most practical ways to secure Modbus traffic is by placing it behind a firewall, which restricts access to only trusted sources and destinations. While VPNs and user access controls can add security, firewalls provide critical segmentation, which is explicitly recommended for legacy and insecure protocols like Modbus.

The NIST Cybersecurity Framework (CSF) is explicitly designed to be flexible, voluntary, and sector-agnostic, making it suitable for diverse environments — including multinational corporations operating in multiple regulatory jurisdictions.

“The Framework is intended to be used by organizations of all sizes, across all sectors and countries. It is technology-neutral and allows for continuous improvement through its tiered implementation and feedback loop.”

— NIST Cybersecurity Framework v1.1, Section 1.2 – Framework Overview

This flexibility allows organizations to tailor their implementation to fit their risk appetite, regulatory requirements, and industry practices.

Per ISA/IEC 62443-2-1 and 62443-2-3, proper patch management is part of operational cybersecurity. For high-priority or critical security patches, the best practice is to apply the patch at the earliest possible opportunity, often during the next available unscheduled or scheduled outage.

“Asset owners shall define procedures for evaluating and applying patches based on criticality and potential impact. High-priority patches should be applied at the earliest opportunity, preferably at the first available system downtime.”

— ISA/IEC 62443-2-3:2015, Clause 6.1 – Patch Management Process

Waiting unnecessarily or skipping patches because "nothing is broken" is not acceptable in security-critical environments.

ICS-CERT (Industrial Control Systems Cyber Emergency Response Team) issues alerts to inform critical infrastructure owners and operators about newly discovered vulnerabilities, threats, and mitigation strategies.

“ICS-CERT Alerts provide timely information to critical infrastructure owners and operators concerning current security issues, vulnerabilities, and exploits.”

— ICS-CERT Advisory Documentation (now under CISA)

Alerts may be sector-wide or vendor-specific, and are part of the U.S. Department of Homeland Security’s proactive cyber defense strategy.

Clarification of Options:

Not specific to the energy sector only (D is too narrow)

Not promotional in nature (eliminates A and B)

According to ISA/IEC 62443-1-1, a vulnerability is defined as “the potential for violation of security,” which means a weakness or gap in protection efforts that could be exploited by threats to gain unauthorized access or cause harm to an IACS. It does not specifically mean an event (B) or a result (D), and it is broader than just management flaws (A). The identification and management of vulnerabilities are key steps in risk assessment and mitigation in the 62443 framework.

The ISA/IEC 62443 series of standards is divided into four main parts, each covering a different aspect of industrial automation and control systems (IACS) cybersecurity1:

Part 1: Terminology, Concepts, and Models

Part 2: Policies and Procedures

Part 3: System Requirements

Part 4: Component Requirements The part 4 of the series focuses on the requirements for the secure development and maintenance of products that are used in IACS, such as controllers, sensors, actuators, network devices, software applications, and cloud services. The part 4 consists of two standards1:

When using the security level (SL) vector approach in ISA/IEC 62443, each Foundational Requirement (FR) can have its own SL-T value. However, these values must reflect the organization’s specific risk assessment outcomes, not generic or industry default values.

“SL vectors should be derived based on the asset owner’s own risk matrix and risk tolerance, ensuring that the security levels support operational needs and business requirements.”

— ISA/IEC 62443-3-2:2020, Clause 6.5.2 – SL-T Vector Selection

Misalignment could lead to over- or under-protection of critical zones or conduits.

CCSC stands for Common Component Security Criteria, as defined in ISA/IEC 62443-4-2. These are a standardized set of technical security requirements that apply across all component types (e.g., embedded devices, software apps, network components).

“CCSCs represent baseline technical security requirements that are commonly applicable to all IACS components, regardless of their type.”

— ISA/IEC 62443-4-2:2018, Clause 4.1 – Common Component Security Criteria

These requirements support consistency and interoperability in component security evaluations.

Foundational Requirement 1 (FR 1) in the ISA/IEC 62443 series is titled “Identification and Authentication Control (IAC)”. Its purpose is to control access to selected devices by ensuring that only authenticated and authorized users or systems can interact with critical IACS components.

“FR 1 – Identification and Authentication Control (IAC): This foundational requirement ensures that all users and components interacting with the system are uniquely identified and authenticated before access is granted.”

— ISA/IEC 62443-3-3:2013, Clause 4.2.1 – FR 1

This foundational layer supports higher-level security goals like use control, confidentiality, and system integrity.

The Triton (also known as Trisis) malware specifically targeted and compromised Safety Instrumented Systems (SIS), disabling the emergency shutdown capabilities at a petrochemical plant. This attack demonstrated that safety systems, once considered isolated and secure, are vulnerable to sophisticated, targeted cyberattacks. Neither Zeus, Stuxnet, nor WannaCry had this specific impact on emergency shutdown safety systems.

 Network security is important in IACS environments because PLCs, or programmable logic controllers, are devices that control physical processes and equipment in industrial settings. PLCs under cyber attack can have costly and dangerous impacts, such as disrupting production, damaging equipment, compromising safety, and harming the environment. Therefore, network security is essential to protect PLCs and other IACS components from unauthorized access, modification, or disruption. The other choices are not primary reasons why network security is important in IACS environments. PLCs are not inherently unreliable, but they can be affected by environmental factors, such as temperature, humidity, and electromagnetic interference. PLCs are programmed using ladder logic, which is a graphical programming language that resembles electrical schematics. PLCs use serial or Ethernet communications methods, depending on the type and age of the device, to communicate with other IACS components, such as human-machine interfaces (HMIs), supervisory control and data acquisition (SCADA) systems, and distributed control systems (DCSs). References:

ISA/IEC 62443 Standards to Secure Your Industrial Control System training course1

ISA/IEC 62443 Cybersecurity Fundamentals Specialist Study Guide2

Using the ISA/IEC 62443 Standard to Secure Your Control Systems3

Programmable Logic Controllers (PLCs) were originally designed to replace relay-based control systems in industrial automation. Early manufacturing and process control systems relied on hard-wired relays, timers, and sequencers, which were inflexible and difficult to modify. PLCs offered a software-based alternative that could easily be reprogrammed for various automation tasks, making plant operations more efficient and flexible. Their purpose was not specifically to enhance network security or Ethernet functionality, but rather to modernize and simplify control logic implementation.

The document titled “Patch Management in the IACS Environment” corresponds to IEC TR 62443-2-3, which belongs to the Policies and Procedures category of the ISA/IEC 62443 series.

IEC TR 62443-2-3 is a technical report providing guidance for managing software updates and patches in IACS environments without disrupting critical operations.

From the IEC 62443 document structure:

“The -2-x family of documents focuses on policies and procedures, especially in relation to the asset owner responsibilities within a CSMS (Cyber Security Management System).”

IEC TR 62443-2-3 specifically describes:

“Recommended practices for planning and executing the patch management process for industrial control systems in a structured and secure manner.”

Incorrect Options:

A. System – System-level requirements are found in 62443-3-x.

B. General – General documents include 62443-1-x, focused on terminology and concepts.

C. Component – Component requirements are covered in 62443-4-x documents.