=Paper= {{Paper |id=Vol-3156/paper29 |storemode=property |title=The Model for Calculating the Quantitative Criteria for Assessing the Security Level of Information and Telecommunication Systems |pdfUrl=https://ceur-ws.org/Vol-3156/paper29.pdf |volume=Vol-3156 |authors=Sergiy Gnatyuk,Oleksiy Yudin,Viktoriia Sydorenko,Tetiana Smirnova,Artem Polozhentsev |dblpUrl=https://dblp.org/rec/conf/intelitsis/GnatyukYSSP22 }} ==The Model for Calculating the Quantitative Criteria for Assessing the Security Level of Information and Telecommunication Systems== https://ceur-ws.org/Vol-3156/paper29.pdf
The Model for Calculating the Quantitative Criteria for Assessing
the Security Level of Information and Telecommunication Systems
Sergiy Gnatyuka,b, Oleksiy Yudinb, Viktoriia Sydorenkoa, Tetiana Smirnovac and Artem
Polozhentseva
a
     National Aviation University, 1, Liubomyr Huzar Ave, Kyiv, 03058, Ukraine
b
     State Scientific and Research Institute of Cybersecurity Technologies and Information Protection, 3, Maksym
     Zaliznyak Str, Kyiv, 03142, Ukraine
c
     Central Ukrainian National Technical University, 8, Universytetskyi Ave, Kropyvnytskyi, 25000, Ukraine

                 Abstract
                 The subject of the article is methods and models for assessing the criticality of industry
                 information and telecommunication systems (ITS). The purpose of the article is to analyze the
                 existing methods and models for assessing the ITS criticality level and, based on the results, to
                 propose a functional model for assessing the ITS security level. Based on the existed method
                 of hierarchy analysis, a functional model for calculating the quantitative criteria for assessing
                 the security level of the ITS was proposed. The model allows to obtain a quantitative score of
                 the security level through the processing of expert evaluations. This simplifies the expert
                 selection procedure, helps to avoid the specifics of expert data processing, and makes it
                 possible to evaluate the ITS with limited statistical data. The conducted study revealed that the
                 developed model for calculating the quantitative criteria for assessing the security level of the
                 ITS, allows experts to focus on the problem by using pairwise comparisons In addition, the
                 proposed model has a built-in criteria for assessing the quality of the expert's analysis and
                 makes it possible to move from a qualitative assessment, in the form of an ordered series of
                 alphanumeric combinations, to a quantitative assessment, which presented as a ratio of the
                 basic security profile to the security profile defined by the expert.

                 Keywords 1
                 Information and telecommunication system, critical information infrastructure, security
                 assessment criteria, functional security profile.


1. List of abbreviations
   Confidentiality:
CT – trusting confidentiality; СА – administrative confidentiality; CO – object reuse; CC – hidden
channels analysis; CE – confidentiality in the exchange.
   Integrity:
IT – trust integrity; IA – administrative integrity; IR – recovery; IE – integrity in exchange.
   Availability:
AR – use of resources; AF – resistance to failures; AQ – quick replacement; AD – disaster recovery.
   Observability:
ON – registration; OI – identification and authentication; OC – reliable channel; OD – segregation of
responsibilities; OP – integrity of the Complex of means of protection; OT – self-testing; OE –
identification during exchange; OS – sender authentication; OR – recipient authentication.

IntelITSIS’2022: 2nd International Workshop on Intelligent Information Technologies and Systems of Information Security, March 24–26,
2022, Khmelnytskyi, Ukraine
EMAIL: s.gnatyuk@nau.edu.ua (S. Gnatyuk); alex@ukrdeftech.com.ua (O. Yudin); v.sydorenko@ukr.net (V. Sydorenko); t.smirnova@gmail.com
(T. Smirnova); artem.polozhentsev@gmail.com (A. Polozhentsev).
ORCID: 0000-0003-4992-0564 (S. Gnatyuk); 0000-0002-4730-1463 (O. Yudin); 0000-0002-5910-0837 (V. Sydorenko); 0000-0003-2897-
0079 (T. Smirnova); 0000-0003-0139-0752 (A. Polozhentsev).
              ©️ 2022 Copyright for this paper by its authors.
              Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
              CEUR Workshop Proceedings (CEUR-WS.org)
2. Introduction
    Global trends in increasing the number and complexity of cyberattacks have led to the actualization
of the need to protect the industry ITS, which are critical for the society, the socio-economic
development of the state and for ensuring the information component of the national security of any
state. Considering the requirements of the national security and the necessity to implement a systematic
approach for handling the problem of critical infrastructure protection at the national level [1], creation
of a system for the protection of the critical infrastructure is one of the priorities in the reformation of
the defense and security sector of Ukraine. Given that, the main problems that should be solved are: the
lack of common criteria for classifying the ITS as critical infrastructure; the lack of a common
methodology for assessing threats to the ITS of critical infrastructure facilities.
    It should be noted, that according to the Law of Ukraine “On the Fundamentals of Cybersecurity of
Ukraine [2] there is a need to form a list of critical information infrastructure facilities and the need to
develop criteria and procedures for classifying the ITS as critical infrastructure, and according to the
Decree of the President of Ukraine No. 96/2016 “On the Decision of the National Security and Defense
Council of Ukraine of January 27, 2016 “On the Cyber Security Strategy of Ukraine” [3], cybersecurity
of critical infrastructure should consist primarily of determining the criteria for classifying information
(automated), telecommunications, and the ITS as critical information infrastructure. Therefore, legal
acts of Ukraine declare the need to develop common criteria and methodology for classifying the ITS
as critical infrastructure facilities. At the same time, the usage of the qualitative assessments is
complicated due to their difficulty of comparison and reproduction. First of all, this is caused by the
complexity of expert selection and the specifics of processing the experimental data.
    The above limitations indicate that there is an important scientific challenge of determining the
criteria for classifying the ITS as a critical information infrastructure. This problem has international
character as well as it is important for both science and practice today.
    The purpose of the study is to propose a functional model for assessing the security level of the ITS
based on the results of existing methods and models analysis for assessing ITS criticality.

3. Literature Review
    In order to determine the optimal method for calculation of the quantitative criteria for assessing the
security of the ITS, the analysis of existing decision-making methods was conducted.
    Decision-making methods are applied in case of absence of the comprehensive information about
the object of the study (ITS). Decision-making methods can be classified according to the content and
type of expert information that was obtained during the analysis [4-6]. Such classification is given in
Table 1 [5]. The first three of the mentioned groups are related to the methods of decision-making
process under conditions of certainty, and the fourth to the methods of the decision-making process
under uncertainty. The most prospective [5] are the following methods: 1) Expected utility hypothesis;
2) Hierarchy analysis; 3) The theory of fuzzy sets
    According to the method of expected utility hypothesis, each possible action generates consequences
characterized by a particular set of properties, factors, or indicators. That particular alternative should be
chosen, the consequences of which are the most preferable. Applying this method, it is necessary to obtain
quantitative score of all possible outcomes, which is the result of decision-making processes. Once it done,
the best result based on these scores should be chosen. In general, this method consists of five steps [6]:
1) Initial analysis. At this step, some possible options of actions that can be performed in the decision
process are identified. 2) Structural analysis. Structuring the problem on a qualitative level. For this
purpose, a decision tree should be built. The decision tree has two types of vertices: solutions and cases.
In vertices-decisions the choice depends on the expert, and in vertices-cases the expert could foresee the
choice with a certain probability. 3) Uncertainty analysis. At this step, the decision should be made to set
the probability values for those branches on the decision tree that start from the node-evidence. All
acquired probability values are subject to consistency validation. 4) Utility analysis. This step requires the
quantitative scores of the utility consequences of the results, which are associated with the implementation
of a particular path in the decision tree. 5) Optimization Procedure. The optimal strategy of action may be
found by calculating the maximum level of the expected utility over the entire set of possible outcomes.
The main advantage of the method is the ability to find the best solution under the risk conditions. But,
on the other hand, the methods of expected utility hypothesis have some disadvantages, namely: time
consuming process, associated with the collection of information on the advantages and probability
distributions related to the effects [7]; the need to involve some additional analysts; lack of mechanisms
to verify experts’ decision. Also, the disadvantages according to [8-9] should include that: experts do not
structure the problem holistically, as it is expected in the theory; experts do not process information,
especially probability, according to the principles of expected utility; expected utility theory poorly
suggests human behavior when they have to make decisions in laboratory tests.

Table 1
Classification of the decision-making methods based on content and type of expert information
 No. Content            of Type of information        Decision making method
        information
        Expert
                                                      The method of domination
 1      information is      -
                                                      Method based on global criteria
        not required
                                                      Lexicographic ordering
                                                      Comparison of differences in criteria
                            Qualitative information;  Convolution methods on the hierarchy of
                            Quantitative assessment   criteria
        Information on
                            of the superiority of the Efficiency-cost methods
 2      superiority on a
                            criteria                  Methods of the thresholds
        set of criteria
                            Quantitative information Methods of the ideal point
                            on substitution           Methods of indifference curves
                                                      Methods of value theory

                                                          Methods of mathematical programming
       Information on      Estimation of the
                                                          Linear and nonlinear convolutions with an
 3     the benefits of     advantage of pairwise
                                                          interactive way to determine its parameters
       alternatives        comparisons
                                                          Methods with discretization of uncertainty
                                                          Stochastic dominance
                           Lack of information about      Methods of decision-making in conditions of
                           the benefits                   risk and uncertainty based on global criteria
       Information on
                           Quantitative information       Method of analysis of hierarchies
       the benefits of
                           on the consequences            Method of decision matrices
       many criteria
 4                         Qualitative information        Methods of fuzzy set theory
       and the
                           about the benefits and         Method of practical decision-making
       consequences
                           quantitative information       Methods of indifference curves for decision
       of alternatives
                           about the consequences         making in conditions of risk and uncertainty
                                                          Methods of decision trees
                                                          Decomposition methods of the theory of
                                                          expected utility

    The method of hierarchy analysis is a mathematical tool for a systematic approach for solving
complex decision-making problems. It also implements a procedure for the synthesis of priorities,
which are calculated on the basis of the expert’s decisions. This method allows the expert to find a
solution (alternative) to the problem that would be better consistent with his understanding of the issue
and the requirements for its solution. In general, this method consists of five steps [10]: 1) Construction
of a qualitative model of the problem, which includes the goal, alternative options for achieving the goal,
and criteria for assessing the quality of the alternatives. The model is described by a means of a hierarchy;
2) Determination of the values of all hierarchy parts with the implementation of the method of pairwise
comparisons. A matrix of pairwise comparisons should be formed; 3) Synthesis of the global alternative
priorities and obtaining a vector of priorities; 4) Verification of the decisions of the experts on consistency
by assessing the level of consistency of the matrix of pairwise comparisons; 5) Obtaining the value of the
best alternative and making a decision. The advantages of the method are [11]: the usage of pairwise
comparisons, which allows the expert to focus on the problem; additionality of the original matrix;
availability of the verbal and numerical scale; built-in criteria for the assessment of the quality of the
expert's work, which is the consistency index, which provides information about the violation of numerical
and transitive consistency of the made decisions. It should be noted, that the method is not devoid of the
following drawbacks [12-14]: evaluation and comparison of more than nine [13] or ten [14] objects
(criteria, alternatives). With increasing the number of objects, the complexity of constructing a
homogeneous matrix of pairwise comparisons increases. Also, limitations are caused by the psychological
capacity of an expert to compare and rate a large number of objects; the appearance of the reverse rank
effect, which means changing the order of previously comparable alternatives by adding new or deleted
existing ones; the usage of the scale of relations, which is a rank multiple of a unit scale.
    The methods of fuzzy set theory consist of formalizing the input parameters by means of a vector of
interval values (fuzzy interval), and getting into each interval is characterized by some level of
uncertainty. The limits of the possible parameters and their most possible values are determined on the
basis of the output data, experience and intuition of the expert. Thus, the basic characteristic of one or
another method is the membership function with the interval parameter [15]. There are a lot of methods
for determining the membership function, e.g., pairwise comparisons, expert evaluations, linguistic
terms based on statistical data, parametric and interval evaluations [16]. The mentioned methods can
be classified as direct or indirect [17]. In direct methods the expert directly sets the rules for determining
the membership function, for example, the methods are based on a probabilistic interpretation of the
membership function. On the other hand, the in indirect methods the expert select the values of the
membership function in the way that satisfies the predetermined requirements, for example, the large-
square method. The advantages of the fuzzy set methods are [18-21]: the ability to evaluate the
alternatives sufficiently objectively by an individual criteria; the ability to include qualitative values in
the analysis, to operate with the fuzzy input data and linguistic criteria; At the same time, these methods
have some disadvantages, as follows [17; 22-23]: there is a subjectivity in the choice of the membership
functions and the formation of fuzzy set rules, and therefore the type of function depends significantly
on the available information and the nature of the problem; the information about the correlation of the
criteria should be given; each method has its own limitations and specifics, and the expert must know
the scope of each method; most of the fuzzy set methods show a weak stability of the results with
respect to the input data. Rule-based methods have the greatest stability under such conditions. Given
the above, it is recommended to apply the method of hierarchy analysis to calculate the quantitative
criteria for assessing security.

4. The Model for Calculating the Quantitative Criteria for Assessing the
   Security Level
   The model for calculating the quantitative criteria for assessing the security level of the ITS, allows
to move from a qualitative assessment in the form of an ordered series of alphanumeric combinations
[24], which indicate the levels of implemented services, to a quantitative assessment as a ratio of the
basic security profile to the security profile determined by the expert, based on the use of the hierarchy
analysis method. The input data for the model are the basic Functional Security Profile (FSP) [25] and
the FSP that has been corrected by the expert. The Normative Documents in the field of Technical
Protection of Information of Ukraine (ND TPI) 2.5-005-99, which defines the standard FSP of the
processed information, defines the requirements for the protection of certain information from some
threats and functional services and allows to counter these threats and ensure compliance with the
requirements [26]. Given the limitations of the hierarchy analysis method in assessing no more than
nine to ten criteria, the groups of criteria for assessing information security will be formed (Fig. 1) [27-
29]. As it is shown, the largest criteria group of the second level is the observation criteria, which may
include up to 9 criteria. The criteria groups of all other levels count from four to five criteria. Therefore,
the method of hierarchy analysis may be used to analyze certain criteria.
Figure 1: Groups of criteria for assessing the security of information for availability and observability
   A flowchart of the model for calculating the quantitative criteria for assessing the security level of
the ITS, based on the use of the hierarchy analysis method, is shown in Fig. 2.




Figure 2: Flowchart of the model for calculating the quantitative criteria for assessing the security level
of the ITS

    The hierarchy analysis method for determining the ratio of alternatives (the basic FSP and the FSP
defined by the expert) is performed in the following way:
    Step 1. The matrices of pairwise comparisons should be constructed for each level of criteria
(security criteria is a level 1, security service criteria is a level 2, security service level criteria is
a level 3):
                                               A = aij     ,                                            (1)
                                                       nxn

where aij = wi w j , wi is the value of the i-th criteria.
   At the same time, a ji = 1 aij , and aii = 1. , which means that the matrix is positive inversely
symmetric.
   To determine the value, the following Table 2 of relative importance will be used.
   For the security service criteria, matrices of pairwise comparisons are compiled. There are up to 4
matrices in total. For security level criteria, the maximum number of matrices can be 22.
   Step 2. The set of eigenvectors of the matrix should be calculated by the geometric mean for each
row of the matrix:
                                     ai = n ai1  ai 2  ai 3  ain = n  j =1 aij ,
                                                                            n
                                                                                                        (2)
where n is a dimension of the matrix.
   Step 3. The results should be normalized, and the normalized priority vector will be obtained:
                                               a
                                         ai = n i ,                                                          (3)
                                             ajj =1

   Step 4. Consistency of local priorities should be checked. Calculation of the largest eigenvalue of
the matrix should be performed:
                                                       n
                                           Ai =  aij ,                                                      (4)
                                                   i =1

                                           Ai = Ai aij ,
                                                                                                             (5)
                                                            n
                                           max =  Ai,                                                     (6)
                                                           i =1

   Calculation of the consistency index:
                                        max − m
                                         Jp =    ,                                                           (7)
                                          m −1
where m is the number of compared elements (matrix size).

Table 2
Scale of relative importance of criteria
                      Verbal assessment of the                              The Value aij
                               expert
                      wi absolutely better than wj                               9
                    wi significantly better than wj                              8
                         wi much better than wj                                  7
                             wi better than wj                                   6
                      wi strongly predominant wj                                 5
                           wi predominant wj                                     4
                       wi slightly predominant wj                                3
                   wi insignificantly predominant wj                             2
                       the criteria are equivalent                               1
                   wj insignificantly predominant wi                            1/2
                       wj slightly predominant wi                               1/3
                           wj predominant wi                                    1/4
                      wj strongly predominant wi                                1/5
                             wj better then wi                                  1/6
                         wj much better than wi                                 1/7
                    wj significantly better than wi                             1/8
                      wj absolutely better than wi                              1/9

   For the security criteria the comparison matrix will be as shown in Table 3.

Table 3
The Matrix for security criteria
                       Confidentiality                          Integrity         Availability   Observability
 Confidentiality              a11                                   a12                a13            a14
    Integrity                 a21                                   a22                a23            a24
   Availability               a31                                   a32                a33            a34
  Observability               a41                                   a42                a43            a44

   The consistency index should be checked by calculating the AC consistency ratio using the formula:
                                                       Jp
                                           Ac =                 ,                                            (8)
                                                       Rc
where Rc is the table value (Table 4).
   Step 5. Calculation of the global priority for the high-level criteria. The normalized priority vector
for each lower-level criteria is multiplied by the normalized priority vector of the higher-level criteria.
The products are summed at the higher level.
                                                       n
                                                Gi =  ai bi ,                                            (9)
                                                      i =1

where n is a number of the security level criteria.

Table 4
Random consistency for matrices of order 2-9
                           Matrix size (n) Random consistency (RC)
                                  2                  0
                                  3                0,58
                                  4                 0,9
                                  5                1,12
                                  6                1,24
                                  7                1,32
                                  8                1,41
                                  9                1,45

   If Ac  0,10, then the data in the comparison matrix are subject to review and refinement.
   Step 6. Determining the ratio of alternatives (the basic FSP and the FSP defined by the expert). For
each FSP, a global priority should be calculated for the confidentiality, integrity, availability, and
observability. The ratio of these global priorities, which describe the quantitative criteria, can be
represented in the form of an expression:
                                                           GFPZ B
                                              VK AHP =              ,                                   (10)
                                                           GFPZ E
where GFPZ B is the table value of the FSP for the industry ITS, and GFPZ E is the FSP, which was obtained
by the expert, using the structural-logical model and the structural-functional method of formation of
the FSP of the industry ITS.
   The implementation of this model allows to move from the qualitative characteristics of security to
the quantitative ones. Proposed model can be used for real ITS in critical infrastructure to calculate its
security level.

Conclusion
    In this paper, the analysis of existing decision-making methods for determining the optimal way for
calculating the quantitative criteria for assessing the security of the ITS was conducted. The methods
of expected utility theory, methods of hierarchy analysis and methods of fuzzy sets theory were
investigated. Taking into account the main advantages and disadvantages of the mentioned methods, it
is advisable to use the methods of hierarchy analysis to calculate the quantitative criteria for the security
assessment.
    The model for calculating the quantitative criteria for assessing the security level of the ITS, which
is based on the use of the method of hierarchy analysis, was developed. This model works by using the
pairwise comparisons, which allows the expert to focus on the problem. Also, the model has built-in
criteria for assessing the quality of the expert's analysis. It is the consistency index, which provides
information on the violation of numerical and transitive consistency of ratings. In addition, the
developed model makes it possible to move from a qualitative assessment, in the form of an ordered
series of alphanumeric combinations, which indicates the level of realized services, to a quantitative
assessment in the form of the ratio of the basic security profile to the security profile determined by the
expert. In further works it is planned to carry out an experimental study of the developed model for
calculating the quantitative criteria for assessing the security level of the ITS.

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