## 2 Materials and Methods
### Security Requirements According to ISO/IEC62443
#### 2.3.1 IEC 62443 Categories  
The standard is based on four main categories; these categories are described in the following section. **Category1--General**  
The first category of this series is General, which includes discussion and topics common throughout the entire series [14]. The second category of this series is Specific. The International Electrotechnical Commission (IEC) Technical Specification 62443-1-1 provides the terminology, concepts, and models for IACS security. The descriptions of terminology and acronyms used during the IEC 62443 standards are provided in IEC/TS 62443-1-2. There are seven foundational requirements (FRs) presented in this standard as follows [17]:  
**FR1: Identification and Authentication Control (IAC):** The primary goal of the identification and authentication control is to verify a user's identity before providing permission to access a system or a resource. Depending on the circumstances, this permission could be  
Figure 1: Risk treatment options. granted to humans, processes, software, or hardware devices that require authorization to access a system [18]. **FR2: Use Control (UC):** This fundamental requirement ensures that only authorized users have access to the system. Its purpose is to prevent unauthorized system activities by verifying that the requested permission has been granted before enabling any entities to initiate communicating with the system [18]. **FR3: System Integrity (SI):** Individuals, procedures, software, and hardware are all examples of authorized entities who may attempt to compromise any component of a system's security integrity [18]. **FR4: Data Confidentiality (DC):** In order to prevent the illegal disclosure of data over communication channels or data storage in repositories, data confidentiality is an essential consideration [18]. **FR5: Restricted Data Flow (RDF):** Security zones and conduits for communication channels are used to restrict the flow of unnecessary data by establishing security borders, which are also known as security zones [18]. **FR6: Timely Response to Events (TRE):** Create reports to respond to any malicious activities detected on a system [18]. **FR7: Resource Availability (RA):** Protect against various kinds of denial-of-service attacks so that a system remains operational [18]. **Category2--Polices and Procedures**  
This category deals with the security of the IACS, and it provides security requirements that can be applied to determine the amount of protection provided by operational IACS [14]. The IEC 62443-2-1 specifies who owns an asset for IACS and provides the parameters for developing and maintaining a cybersecurity strategy. This series covers the capabilities of the protection system that are required to ensure the proper operation of an IACS. IEC/IS 62443-2-2 defines a methodology and framework for an IACS for assessing defense in accordance with the security level and ensuring that the corresponding processes are implemented. The third series in this category is IEC/TR 62443-2-3, which provides information about the exchange of information from asset owners to product suppliers. The next series provides information about the IACS service provider and asset owner [17]. **Category3--System**  
The IEC 62443-3-1 standard gives an overview of the advantages and drawbacks of currently available network security solutions. The IEC 62443-3-2 standard addresses the assessment of security risks and the design of network architectures and systems. Part 3-3 of the standard defines broad system security requirements, with an emphasis on ensuring that system performance is not compromised during the process of fulfilling these requirements [19]. **Category4--Component**  
It comprises two documents that make up the Component group. IEC 62443-4-1 specifies the development procedure for ICS products to restrict the number of security vulnerabilities in control systems solutions. It is specified in the IEC 62443-4-2 standard how to secure the separate components of an ICS network in terms of their technical requirements.