RU2642374C1 - Method for construction of computer attack protection system for automated control systems - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: invention relates to the field of protection systems for automated control systems for various purposes from information and technical effects and can be used to build systems to protect automated control systems (ACS) from one of the main types of information and technology impacts – computer attacks. Technical result is achieved due to the use of the method of constructing a system for protection of ACS from computer attacks, which includes a step of forming a set of all possible versions of building subsystems of the system for protection of ACS from computer attacks, a step of forming a set of all possible versions for building a system for protecting ACS against computer attacks, a step of estimating the cost and required resources of versions for building a system for protecting ACS against computer attacks, a step of estimating efficiency of versions of building a system for protection of ACS from computer attacks and step of estimating the degree of impact of versions of building the protection system on the performance of the protected ACS.

EFFECT: obtaining the most effective version of building a system for protecting ACS from computer attacks with the least impact on the performance of the protected ACS.

1 cl, 3 dwg

Description

The invention relates to the field of protection systems for automated control systems for various purposes from information and technical influences and can be used to build protection systems for automated control systems (ACS) from one of the main types of information and technical effects - computer attacks.

To ensure the security of the ACS from computer attacks, various technical measures are applied, which are implemented in the form of protection systems.

According to [1], technical measures to protect information (from the point of view of protection against computer attacks) implemented in the ACS as part of its protection system should provide:

• identification and authentication of access subjects and access objects;

• access control of access subjects to access objects;

• restriction of the software environment;

• protection of computer storage media;

• registration of security events;

• anti-virus protection;

• detection (prevention) of intrusions;

• control (analysis) of information security;

• integrity of the automated control system and information;

• availability of technical equipment and information.

At the same time, the implementation of the indicated technical measures within the framework of the ACS protection system against computer attacks should not adversely affect the normal operation of the ACS (i.e., it should not reduce the performance of the ACS).

Based on these requirements, the task of constructing an ACS protection system from computer attacks is reduced to the task of selecting such structures and parameters of an ACS protection system from computer attacks so that a protection system that meets the selected structure and parameters allows for a minimal impact on the performance of the protected ACS while maintaining the required level of protection from computer attacks and met the requirements for cost and resources consumed.

The prior art method for automated control of the process of designing the structure of the control system of technical systems and a device for its implementation [2], which can be used for designing multi-parameter objects.

The disadvantage of these methods and devices is their narrow specialization - the design of control systems for technical systems of various classes, which does not allow the construction of a control system for automated control systems against computer attacks.

There is also known a method and device for choosing the preferred means of information protection [3], based on the use of the estimated sample, consisting of normalized individual quality indicators that allow you to create two standards E _with - with an average statistical level of quality and E _l - the level of best quality. Based on the use of these standards, the preferred facility with the highest comprehensive quality indicator is selected from the totality of the evaluated means.

The disadvantage of these methods and devices is the impossibility of their use in building a system for protecting ACS from computer attacks, consisting of several interconnected elements, taking into account their influence on the performance of the protected ACS.

The aim of the invention is to obtain the most effective option for constructing a system for protecting ACS from computer attacks with the least impact on the performance of the protected ACS.

To achieve the purpose of the invention, it is proposed to use a method of constructing a system of protection against computer attacks for automated systems based on the decomposition of the task of choosing the rational structure and parameters of the protection system of an automated control system against computer attacks according to the sequence of procedures for generating options for constructing a protection system and subsystems of the protection system (functional decomposition).

Decomposition by subsystems is based on the fact that the ACS protection system from computer attacks can be represented as a set of subsystems that solve certain problems and implement a certain list of functions. Proceeding from this, as the subsystems ensuring the security of the ACS from computer attacks as part of the protection system, we can distinguish:

• a subsystem for detecting computer attacks;

• a subsystem to counter computer attacks;

• a subsystem to eliminate the consequences of computer attacks.

In FIG. Figure 1 shows the decomposition of the protection system into subsystems in accordance with the goals and objectives of the protection system, and also shows how to solve the problems of each subsystem.

In FIG. Figure 2 shows the correlation of methods for solving problems by subsystems of the protection system with technical measures of protection against computer attacks.

The decomposition according to the sequence of procedures for the formation of options for building a protection system will have the following form:

• the formation of sets of V _obn , V _pr , V _{device of} all possible options A _obn , A _pr , A _{device of the} construction of each subsystem:

,

,

,

,

,

,

where V _obn - the set of all possible options for building a subsystem for detecting computer attacks;

V _ol - the set of all possible options for building a subsystem to counter computer attacks;

V _device - the set of all possible options for constructing a subsystem to eliminate the consequences of computer attacks;

N, M and K - the number of all possible options for building subsystems for detecting computer attacks, countering computer attacks and eliminating the consequences of computer attacks, respectively;

• the formation of the set V of all possible options And the construction of the protection system based on the sets of V _obn , V _ol , V _{device of the} set of options for the protection system:

,

,

where S is the number of all possible options for constructing a protection system;

• assessment of the generated set of V options A for building a protection system and the allocation of a subset of V * options A * from it, satisfying the requirements for cost and consumed resources;

• assessment of the formed set of V * options A * of building a security system that satisfies the cost and resources consumed and allocating from it a subset of V ** options A ** of building a security system that meets the security requirements;

• assessment of the generated set of V ** options A ** for building a security system that meets security requirements, and choosing from a rational option A 'for building a security system that has minimal impact on the performance of the protected ACS.

The general scheme of the process of choosing a rational option for constructing an ACS protection system against computer attacks is presented in FIG. 3.

The initial data for building a system for protecting ACS from computer attacks are:

• the required effectiveness of the ACS protection system from computer attacks Q * expressed by a set of indicators characterizing the ability of the protection system to provide minimal risk from computer attacks and the recoverability of the ACS after computer attacks;

• maximum allowable cost C _{add to} create a system of protection against computer attacks;

• the maximum allowable resources required for the functioning of the protection system R _add .

At the stage of formation of the sets of all possible options for building subsystems, the formation of the set of all possible options for building a subsystem for detecting computer attacks, the sets of all possible options for building a subsystem to counteract computer attacks and the set of all possible options for building a subsystem for eliminating the consequences of computer attacks.

The morphological analysis method [4] was used to form these sets, the advantage of which is the possibility of simple algorithmization and computer implementation.

A variant of each subsystem is formed on the basis of the structure of the subsystem, which is a set of elements of the L subsystem that implement methods for solving the problems of the subsystem and the set of parameters F of the subsystem, and many of these options are formed by enumerating all possible combinations of combinations of elements of the subsystem and their parameters

For the subsystem for detecting computer attacks, all possible options are formed based on the totality of the sets {L _obn , F _obn }, where L _obn is the set of all existing means of detecting computer attacks, and F _obn is the set of sets of parameters for each means of detecting computer attacks.

For the subsystem of counteracting computer attacks, all possible options are formed on the basis of the set of sets {L _CR , F _CR }, where L _CR is the set of all existing means of countering computer attacks, and F _CR is the set of sets of parameters for each means of countering computer attacks.

For the subsystem of eliminating the consequences of the use of computer attacks, all possible options are formed on the basis of the set of sets {L _device , F _device }, where L _device is the set of all existing means of backup and recovery of the system and data, and F _device is the set of sets of parameters for each backup tool copy and restore system and data.

To reduce the number of all possible options for constructing each subsystem (in order to reduce time costs), three possible values are accepted for parameters with smoothly changing values: the minimum value of the parameter, the average value of the parameter, and the maximum value of the parameter.

Further, at the stage of formation of the set of all possible options for constructing a system for protecting ACS from computer attacks based on the sets of V _obn , V _pr and V _devices obtained at the previous stage, using the method of morphological analysis, a set of V of all possible options for constructing a protection system by enumerating all possible combinations of combinations of options for building subsystems.

Further, at the stage of assessing the cost and required resources, a set of V * is generated — the options for constructing an ACS protection system from computer attacks that satisfy the cost requirements and the resources required for the functioning of the protection system:

,

,

where C and R are the cost of the protection system and the resources required for the operation of the protection system;

With _additional and R _additional - the maximum allowable cost and required resources.

The cost of the protection system is the sum of the cost of the subsystems that are part of it:

C = C _obn + C _ol + C _device

where C _obn , C _pr , C _{ustr the} cost of the subsystem for detecting computer attacks, the cost of the subsystem to counter computer attacks and the cost of the subsystem to eliminate the consequences of computer attacks, respectively.

R resources, required for the operation of the protection system are determined by two parameters: R _calc - computing resources (the requested amount of memory, processors characteristics and the like) and _humans R - human (required number of personnel required to operate the protection system):

.

.

In the set V * formed at this stage, the options for constructing a protection system are selected whose cost and resources required for functioning do not exceed the maximum allowable C _add and R _add .

At the stage of evaluating the effectiveness of options for constructing a security system from a variety of V *, options are selected for constructing a protection system that satisfy the required level of security provided by the protection system, and a set of V ** is formed from the selected options:

,

,

where Q is a set of indicators characterizing the security level of the ACS, implemented by the protection system;

Q _req - the required level of security for ACS.

As indicators characterizing the ACS protection level from computer attacks, the ACS protection coefficient Z [5] and the ACS recovery time after applying a computer attack T are _used :

.

.

The methodology for determining the protection factor of ACS Z is described in [5]. The essence of the methodology is to conduct ACS testing in two directions: local testing and network. Local testing consists in checking the security status of individual elements of the ACS from an internal intruder. Network testing is to simulate the actions of an external intruder and is aimed at checking the security of the ACS as a whole.

Based on the results of local testing, the local vulnerability coefficient L is determined, which is determined as follows:

,

,

where P _i - the number of open ports on the i-th element of the ACS;

Y _i - the number of ports ix of ACS elements on which vulnerabilities were found.

Based on the results of network testing, the vulnerability coefficient S of a computer network that combines the components of an automated control system is determined:

,

,

where R _i - the number of realized scenarios of computer attacks on the i-th element of the ACS;

E _o - the number of basic scenarios for simulating computer attacks;

And _o is the number of additional scenarios for simulating computer attacks.

Next is the coefficient of the overall vulnerability of the system W, which is determined as follows:

W = L⋅S.

Based on the fact that the level of protection of the automated control system and the level of general vulnerability of the automatic control system complement each other to unity, the security coefficient of the system Z can be defined as:

Z = 1-W.

Recovery time ACS operation after computer attack T _Restore defined as the sum total recovery time of backup _{Restore given} T and the rise time of the operating system from the recovery T _{Restore points. OS:}

T _rev = T _{rev data} + T _{restore wasps}

At the final stage of choosing a rational option for building an ACS protection system from computer attacks from the set V ** obtained at the previous stage, a rational option A 'for building an ACS protection system from computer attacks is selected that provides minimal impact on the performance of the protected ACS:

,

,

where K is a set of indicators for reducing the performance of an automated control system when introducing a system of protection against computer attacks into its composition.

The set of indicators for reducing the performance of the ACS is two complex indicators K _C is a comprehensive indicator of a decrease in the productivity of the technical component of the ACS (a combination of hardware, software and software and hardware of an ACS) and K _P is a complex indicator of a decrease in the performance of maintenance personnel:

.

.

At the same time, the decrease in performance of the technical components of the ACS is evaluated as:

,

,

where K _PS - the coefficient of reduction in throughput (the number of operations performed by the system for a certain period of time);

K _PAIR - reduction coefficient of parallelism (the number of operations performed by the system simultaneously);

K _RES - the coefficient of increase in the reserve of the resource (the amount of resources necessary to ensure the growth of the load);

K _Totkl - coefficient of increase in response time (execution time of one operation);

K _OS - coefficient of increase in the error rate (frequency of generation of a denial of service exception system).

The decrease in productivity of staff, in turn, is assessed as:

,

,

where: K _Tvyp - the coefficient of increase in the time of performing operations by persons of the operating personnel in the performance of their functional duties;

K _D - coefficient of increase of discomfort in the performance of functional duties.

The throughput reduction factor K _PS is determined as follows:

where k _PS - the number of operations performed by the ACS during the time T _isp before the introduction of the system of protection against computer attacks into the ACS;

k ' _PS - the number of operations performed by the ACS during the time T _use after the introduction of the system of protection against computer attacks, the time T _use is determined based on the purpose and performed functions of the protected ACS.

The parallelism reduction coefficient K _PAIR is determined by the formula:

,

,

where k _PAR - the number of operations performed by the ACS at the same time before the introduction of a computer attack protection system into the ACS;

k ' _PAR - the number of operations performed by the ACS simultaneously after the introduction of a system of protection against computer attacks into the ACS.

The coefficient of increase in the resource reserve K _RES is determined by the following formula:

,

,

where k _PEC - computing resources available to ensure the functionality of the ACS before the introduction of a system of protection against computer attacks;

k ' _PEC - computing resources available to ensure the functionality of the ACS after the introduction of a system of protection against computer attacks into the ACS.

The response time increase factor K _Totkl is defined as follows:

,

,

wherein t _'off - the execution time of operations ACS after administration of the automation system of protection against computer attacks;

t off - the time it _{takes to} perform one operation in the ACS before the system of protection against computer attacks is introduced into the ACS.

The coefficient of increase in the error rate K _OS is determined by the formula:

,

,

where k ' _OSh ^{_ the} number of cases of generation of ACS exceptions of the type "denial of service" after the introduction of the ACS protection system against computer attacks;

_OR k ^_ number of generation ACS exceptions such as "denial of service" to the introduction of the automated control system of protection against cyber attacks.

The initial data for calculating the above performance reduction factors for the technical components of the ACS are determined during the trial testing of protection systems built on the basis of possible options for constructing this system using standard performance assessment tools that are part of most operating systems.

The coefficient of increase in the time of performing operations by persons of the operating staff in the performance of their functional duties K _Tvyp is determined by the formula:

,

,

where t ' _vy is the time of the operation by the ACS personnel after the introduction of a system of protection against computer attacks;

t _vy - the time of the operation by the ACS personnel before the introduction of a system of protection against computer attacks into its composition.

The initial data for determining the coefficient of increase in the time of performing operations by persons of the service personnel during the performance of their functional duties are determined during the trial testing of the system by measuring the corresponding time intervals.

The coefficient of increase in discomfort during the performance of functional duties K _D is determined by interviewing users in the process of trial testing on pre-formed questionnaires. Questionnaires are formed by a group of experts on the basis of information about the structure and tasks to be protected by the automated control system.

To ensure the possibility of comparing construction options for one generalized indicator, a convolution of the obtained indicators for reducing the level of ACS performance is performed. Convolution is performed using weight indicators as follows:

,

,

,

,

,

,

where r _c , r _p , r _ps , r _steam , r _res , r _Totkl , r _osh , r _Tvyp , r _d are weighting coefficients of significance at the corresponding performance reduction coefficients, which are determined by a group of experts based on the structure of the protected ACS and the tasks it solves .

Thus, the proposed method will allow you to build a system for protecting ACS from computer attacks that meets the requirements for cost, resource consumption, protection efficiency and having minimal impact on the performance of the protected ACS.

Information sources

1. Methodical document. Information security measures in state information systems: approved. Director of the FSTEC on February 11, 2014 // FSTEC of Russia. 2014.

2. Pat. 2331097, Russian Federation, IPC G05B 17/00, G06F 17/50, G06Q 90/00. The method of automated control of the process of designing the structure of the control system of technical systems and a device for its implementation / Selifanov VA, Selifanov VV, publ. 08/10/2008.

3. Pat. 2558238, Russian Federation, IPC G06F 15/16, G06F 17/00. Method and device for choosing the preferred means of information protection / Shemigon N.N., Chernoscutov A.I., Kukushkin S.S., publ. 07/27/2015.

4. Odrin V.M. Method of morphological analysis of technical systems. - M.: VNIIIPI, 1989.

5. Mukminov V. A., Khutsishvili V. M., Lobuzko A. V. Methodology for assessing the real level of security of automated systems // Software products and systems. 2012. No1 (97). S. 39-42.

Claims (1)

A method of constructing a system of protection against computer attacks for automated control systems, which includes the stage of generating the set of all possible options for building subsystems of the system of protection against computer attacks, during which, using a computer-implemented method of morphological analysis, form the set of possible options for building a subsystem for detecting computer attacks attacks, many possible options for building a subsystem to counter computer attacks and many possible options for the structure of the subsystem for eliminating the consequences of the use of computer attacks, in order to reduce the number of possible options for constructing subsystems for the parameters of elements of subsystems with smoothly varying values, they take the minimum, average and maximum values; the stage of forming the set of all possible options for building a system of protection against computer attacks, during which, using the method of morphological analysis implemented by a computer, based on the sets of possible options for building subsystems obtained at the previous stage, form the set of all possible options for building a system of protection against computer attacks , which is recorded in the computer memory; the stage of assessing the cost and required resources of the options for building a system of protection against computer attacks, during which the computer determines the cost and the resources required for functioning of all options for building the system from the set of options formed at the previous stage, using the computer, choose options, cost and consumed the resources of which do not exceed the set, and further from these selected options form a lot of options for building a system of protection against computer attacks that satisfy the requirements aniyam cost and consumes resources which are recorded in the computer memory; the stage of evaluating the effectiveness of options for building a system of protection against computer attacks, during which using testing with a computer to determine the effectiveness of options for building a protection system from the set formed in the previous step, choose options whose effectiveness is equal to or greater than required, and then from these selected options form many options for building a system of protection against computer attacks that meet the requirements for efficiency, while effectively STIs use the security factor of the automated control system and the recovery time of the automated control system after applying computer attacks; the stage of assessing the degree of influence of the options for building a security system on the performance of the protected automated control system, during which they evaluate the level of decrease in productivity of the protected automated control system when it introduces variants of a system of protection against computer attacks that satisfy the efficiency requirements from the set formed at the previous stage, and choose a rational option to build a system of protection against computer attacks with a minimum level of reduction in production duration of the protected automated control system, while as an indicator of the level of productivity reduction, a comprehensive coefficient of productivity reduction is used, which includes the coefficient of performance decrease of the technical components of the protected system and the rate of performance decrease of the personnel serving the protected system.

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