АНАЛІЗ ЗАГРОЗ І ВРАЗЛИВОСТЕЙ КОМП’ЮТЕРНИХ МЕРЕЖ ТА ОБҐРУНТУВАННЯ КОМПЛЕКСНОГО ПІДХОДУ ДО ЗАБЕЗПЕЧЕННЯ ЇХ КІБЕРБЕЗПЕКИ

The article presents a comprehensive analysis of modern threats and vulnerabilities affecting computer networks in the context of the rapid development of digital technologies and the growing number of cyber threats targeting information infrastructures. Particular attention is paid to the study of architectural and protocol vulnerabilities in computer networks, especially at the data link and transport layers of the Open Systems Interconnection (OSI) model, which are often exploited as initial entry points for sophisticated cyberattacks. The study provides a systematic classification of network threats and attacks according to their nature, origin, and the layer of the network architecture in which they occur. Passive and active attacks, as well as internal and external threats, are analyzed in terms of their impact on the confidentiality, integrity, and availability of information resources. Special emphasis is placed on the analysis of modern network reconnaissance and scanning techniques, which are widely used both by cybersecurity professionals for security auditing and penetration testing and by malicious actors to identify vulnerabilities in network infrastructures. A separate section of the article focuses on the analysis of architectural vulnerabilities at the data link layer caused by the lack of authentication mechanisms in fundamental protocols of the IEEE 802 family. The study describes several common attack techniques based on manipulation of Ethernet frames, including MAC table flooding, Address Resolution Protocol (ARP) spoofing, VLAN hopping, as well as attacks targeting Dynamic Host Configuration Protocol (DHCP) infrastructure and the Spanning Tree Protocol (STP). Considerable attention is also devoted to the analysis of Denial of Service (DoS) and Distributed Denial of Service (DDoS) attacks, which remain among the most widespread and dangerous cyber threats affecting modern information systems. The study also highlights the role of botnets and compromised Internet of Things (IoT) devices in the execution of large-scale distributed attacks. The increasing number of poorly secured IoT devices significantly expands the attack surface and enables cybercriminals to generate extremely high traffic volumes capable of disrupting the availability of critical information resources. Based on the conducted analysis, the article substantiates the necessity of implementing a comprehensive approach to computer network security. Such an approach integrates configuration-based, cryptographic, and organizational security measures implemented at different layers of the network infrastructure. The results of the study may be applied in the development of information security policies, the design of secure corporate network infrastructures, cybersecurity auditing, and the training of specialists in the fields of information technology and cybersecurity.