3. Checking Security KPIs:

The check method is used to assess the security KPIs. It iterates through the KPIs in the KPI dictionary and compares each KPI to the corresponding data from the self.data list; if a security KPI is greater than the corresponding element in the data list, it calls the alert method with the problematic KPI as an argument.

4. Alerting:

The alert method is intended to take appropriate security measures to mitigate vulnerabilities when a problematic KPI is detected. However, implementing this method is incomplete, and it mentions taking measures not defined in the provided code.

5. Creating an Organization and Using the Class:

At the end of the code, an instance of the Secure\_KPI class is created, named organization\_x. Data for the organization are input using the input\_data method.

The security KPIs are calculated and checked using the check method.

Additionally, the database should contain threshold values for the parameters of each layer (Table 3).

Based on the comparison of actual measured (estimated) KPIs with threshold values, a decision is made on the need to improve certain parameters (D), if necessary, based on Decision Rules (DR) matrices for each KPI.

$$D = \begin{cases} Ralle\_1 & \text{if } \quad cond\_1 = true \\ \dots & \dots & \dots \\ Rule\_N & \text{if } \quad cond\_N = true \end{cases}$$

where

$$DR = \begin{pmatrix}Rule1 \ cond\_1 \\ \dots & \dots \\ Ralle\_Ncond\_N \end{pmatrix}$$

where *RuleN* is the action that has to be applied if the condition *condN* is true.

These formulas are introduced to complete the work of the approach in a comprehensive way. In the future, specific rules will be developed for certain conditions corresponding to deviations in the measured indicators.

#### **6. Conclusions**

In conclusion, 5th generation cellular networks actively replace communication in many areas of human life. The number of industries decreases, in which it is impossible or impractical to use 5G networks. Operators of critical infrastructure, special users (such as the police), governments, and the military are not the exception. Modern cellular networks can and must be easily adapted to the needs of special users. In this scenario, the network is subject to more stringent demands regarding reliability, performance, and, most importantly, data security. This scientific article focuses on the challenges related to ensuring cybersecurity.

To effectively increase the level of cybersecurity or ensure its sufficient level, it is necessary to measure the leading indicators of the effectiveness of security systems. At the moment, there are no comprehensive lists of these key indicators that require priority monitoring. Therefore, this article first analyzed the existing similar indicators and presented their list, which will make it possible to continuously monitor the state of cyber security systems of 4G/5G cellular networks with the aim of using them for groups of special users. Therefore, this article proposed a method to determine these indicators and their evaluation. For this method, a meaningful analysis of possible groups of performance indicators was performed, the most relevant ones were selected, and a mathematical apparatus was proposed for their quantitative evaluation. Furthermore, within the framework of solving research problems, improvements were proposed for the core of the 4G/5G network, which allows data and performing statistical analysis at the expense of special sensors and the existing server.

Thus, to improve cybersecurity in critical infrastructure, government, military, and particular user networks using 5G technology, it is necessary to continuously monitor the performance of security systems. The first step is to ensure that the security architecture and practices comply with all the regulations governing the special user groups. After this, it is necessary to continuously monitor the presence of cyber incidents, log any violations, and perform more comprehensive assessments of the cybersecurity parameters in Table 3. If thresholds are exceeded, these assessments should become the basis for making decisions about an immediate response to cybersecurity problems or a comprehensive change to cybersecurity approaches.

Thus, the approach proposed in the article opens up an opportunity for continuous monitoring and, accordingly, improving the performance indicators of cybersecurity systems, which in turn makes it possible to use them for the maintenance of critical infrastructure and other users whose service requires increased requirements for cybersecurity systems.

Future scientific research will be directed toward implementing the proposed method and evaluating its validity. Additionally, there are plans to take advantage of artificial intelligence to process large datasets and make informed decisions based on established rules.

**Author Contributions:** Conceptualization, R.O., M.I., G.I., S.F. and Y.S.; methodology, R.O., M.I., G.I., S.F. and Y.S.; software, R.O., M.I., G.I., S.F. and Y.S.; validation, R.O., M.I., G.I., S.F. and Y.S.; formal analysis, R.O., M.I., G.I., S.F. and Y.S.; investigation, R.O., M.I., G.I., S.F. and Y.S.; resources, R.O., M.I., G.I., S.F. and Y.S.; data curation, R.O., M.I., G.I., S.F. and Y.S.; writing—original draft preparation, R.O., M.I., G.I., S.F. and Y.S.; writing—review and editing, R.O., S.F. and Y.S.; visualization, R.O., M.I., G.I., S.F. and Y.S.; project administration, R.O. and S.F. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** This work was supported by the Shota Rustaveli National Foundation of Georgia (SRNSFG) (NFR-22-14060), the National Scholarship Programme of the Slovak Republic and EU Next Generation EU through the Recovery and Resilience Plan for Slovakia under project No. 09I03-03- V01-000153.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


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