Vol 22, No 3 (2021)

Currently, malware developers are actively using domain name generation technique called DGA to establish communication between malware and its command centers. Domain name generation in accordance with a given algorithm allows malicious software to bypass information protection tools blacklists, thus making blacklists ineffective, and establish a communication channel to receive control commands and parameters, as well as to transfer information from the information system to external resources controlled by the attackers. Thus, it is necessary to develop new approaches to DGA generated domain names detection using DNS traffic of an information system.

During the research, the authors have developed a solution for detecting the information system objects interaction with DGA domains based on the use of machine learning. Detection of this interaction occurs in two stages. On the first stage the classification task is being solved for each DNS name from overall information system DNS stream. On the second stage, for each DNS name classified as a DGA, corresponding DNS query is being enriched using data from external sources and a final decision about the malicious nature of the request to resolve this DNS name is being made, followed by notification of the security administrator via e-mail channels.

The paper describes the process of developing a classifier based on machine learning, defines the input data of the DNS name necessary for classification, presents the results of classifier training on a representative set of test data. The logic of making a decision about the malicious nature of DNS requests has been substantiated. The developed solution was tested using experimental stand. Recommendations for correct classifier operation support are proposed.

Application of the developed solution will make a posteriori detection of information interaction of malicious software working on compromised objects of the information system with the servers of the attackers command and control centers possible.

Structures with an inhomogeneous regular structure (plates, beams, shells) are widely used in engineering, especially in aviation and rocket and space. In calculations for the strength of elastic composite structures using the finite element method (FEM), it is important to know the error of the solution. To analyze the error of the solution, it is necessary to use a sequence of approximate solutions constructed according to the FEM using the grinding procedure for basic discrete models that take into account the non-homogeneous, micro-homogeneous structure of structures (bodies) within the micro-approach. The implementation of the grinding procedure for basic models requires large computer resources.

In this paper, the method of equivalent strength conditions (MESC) for testing the static strength of elastic bodies with an inhomogeneous regular structure, for which sets of different loads are given, is briefly described. According to the MESC, the calculation of the strength of a composite body for which the loading is set is reduced to the calculation of the strength of an isotropic homogeneous body (having the same loading as a composite body) using equivalent strength conditions. In the numerical implementation of the MESC, adjusted equivalent strength conditions are used, which take into account the error of approximate solutions. Here, the MESC is implemented on the basis of the FEM. If a set of different loads is specified for a composite body, then generalized equivalent strength conditions are applied in this case. The procedure for constructing generalized equivalent strength conditions is shown. The calculation of the strength of composite bodies according to the MESC using multigrid finite elements requires  times less computer memory than a similar calculation using crushed basic models of composite bodies. The given example of calculating the strength of a composite beam, for which a set of loads is set, using the MESC using generalized equivalent strength conditions shows its high efficiency.

The article considers a method of assessing and improving main parameters of the computer network efficiency. Reliability is the main criteria for ensuring the required performance of distributed control systems. To improve reliability of the computer network hardware and software redundancy are being used. Software redundancy requires new versions to be developed for software modules in which failures are likely to occur. The article considers the N-version programming and recovery block as methods of introducing software redundancy and, taking the need to develop multiple versions of the same software module into account, estimates the costs of network software development. To implement the proposed approach article presents mathematical reliability model that takes into consideration the architecture of a computer network software and the labor costs that its development is going to require. This model becomes a basis for a software created to research computer network software reliability, which allows to find the dependance of network software reliability on the number of one of its software module versions. Comparison of the changes dynamics of reliability indicators and labor intensity of software development indicated a sufficient amount of software module versions that need to be developed. The article concludes by pointing out the importance of determining the labor intensity of network software development and of its usage in the design of a computer networks in which reliability is being increased through software redundancy.

Recently, there has been an increase of interest in satellite orbit raising using electric propulsion subsystems. Theoretic analyses and practical experience demonstrate that while orbit raising to GEO via a transfer orbit is feasible, it requires a certain amount of time due to electric thrusters’ thrust being low (40-300 mN) and thus incomparable with that of apogee propulsion systems’ liquid propellant thrusters (22-400 N). Due to low thrust, orbit raising by electric thrusters is time-consuming. However, the associated increase in mass to GEO may counterbalance the long duration of satellite commissioning. Calculations demonstrate a potential added satellite mass on GEO of up to several hundred kilograms with orbit raising duration of about 6 months. In particular, with satellite mass not exceeding 2500 kg, coupled launch is possible using existing launch vehicles. ISS took into consideration the positive results obtained with Express-AM5, and Express-AM6 satellites to design the Express-80 and Express-103 with orbit raising in mind. Such approach allowed for a coupled launch on Proton-M carrier rocked with Breeze-M upper stage, and a twofold launch cost saving. To increase thrust during orbit raising and decrease its duration, coupled thruster operation in high thrust mode was implemented. The resulting total mass on GEO increase constituted over 700 kilograms with maneuver duration of up to 158 days. This allows performing coupled launches of heavier satellites with orbit raising by means of electric propulsion in a feasible timeframe.

The formation of an incommensurate three-dimensional magnetic order in an antiferromagnet is studied as a result of a strong correlation between holes and localized spins. The spectrum of spin polarons, the spin density wave, and the wave vector of the structure are calculated in the Kondo lattice model. The magnetic system is considered in the adiabatic approximation, the sublattice magnetization and spin-spin correlation functions are presented in the mean field approximation. The Fermi energy and s–d interaction energy are calculated. The heat capacity and heat capacity anomalies caused by spin polarons have been determined. Anomalies in the temperature dependence of conductivity and in optical conductivity in the low-energy region are founded.

The study of the nanocrystalline state, which significantly changes most of the physical characteristics of substances, is very relevant. Of great practical interest are the works devoted to the study of the magnetic characteristics of nanocrystals of ferromagnetic substances. It has already been shown that the size of iron nanocrystals significantly affects the magnitude of their magnetization. Nevertheless, an adequate model of the structure of nanocrystalline formations consisting of a different number of iron atoms, which allows us to describe the experimentally detected changes in the magnetic characteristics, has not yet been presented.

In this paper, we analyze nanocrystalline iron clusters that are different in configuration and number of their constituent atoms. Spatial models of clusters are constructed using a three-dimensional modeling program, and the coordinates of individual atoms in the cluster are determined. The proposed structures of nanocrystals are based on tetrahedrally densely packed cluster assemblies of iron atoms. The electron state density spectra were constructed for the proposed clusters. For this purpose, the theory of the electron density functional was used, the calculation was carried out by the method of scattered waves in accordance with the band theory of crystals.

It is shown that the appearance of magnetization in tetrahedral densely packed cluster formations is associated with the excited electronic states of the atoms located on the surface of the nanocluster. Excited atoms have an increased electron density, that is, electrons are able to transition to states with higher energy, approaching the Fermi energy. In this case, the Stoner condition necessary for the occurrence of magnetization is fulfilled. The configurations of electrons with spin up and down differ, which is why uncompensated magnetic moments appear. It is confirmed that the proposed models of iron nanoclusters satisfactorily correspond to the known experimental data.

Electrochemical and electrophysical methods of processing metals and alloys have found wide application in mechanical engineering and instrument making, including rocket and space technology. These processing methods have a number of advantages and wide technological capabilities. However, the pace of industrial adoption is still not high, which is largely due to the novelty of these methods.

There are known cases of practical use of linear electrodynamic motors as feed drives for machine tools for the implementation of electrochemical and electrophysical methods of processing metals and alloys, namely, pulse electrochemical processing and electrical contact processing. The linear electrodynamic drive was the best suited for moving the electrode – the tool for each pulse of the process current. The article discusses the basic control schemes for a linear electrodynamic motor. Currently, there is a need to create an engine control unit based on modern electronic components.

The article presents a control system for a linear electrodynamic motor used in an electrical processing installation for copy-piercing operations in the manufacture of dies, molds and other technological equipment. On the basis of modern advances in electronics, a block diagram of the control of an electrical processing unit was developed. The setup is controlled via a personal computer, where the corresponding control program is loaded. This setup provides a system for recording the movement of the electrode – tool using a linear displacement sensor. With this sensor, the control module varies the input parameters that are necessary for machining the workpiece. The sensor is powered directly from the microcontroller. Using the above sensor, the processing depth and the speed of movement of the tool electrode are recorded and analyzed. The article presents the results of checking the operability of the microcontroller with an oscilloscope.

The developed control system with inductive displacement sensors and modern digital technology will make it possible to obtain the positioning accuracy of the tool electrode within a few micrometers, which corresponds to the world level.