\section{Introduction}

In our increasingly interconnected world, securing network infrastructure is paramount. The rapid growth of digital technologies and pervasive reliance on networked systems for critical operations, communication, and data exchange has amplified efficiency but also exposed entities to escalating cyber threats \cite{ref1, ref2}. The integrity, confidentiality, and availability of information are constantly challenged by malicious actors employing sophisticated attack vectors \cite{ref3}. This necessitates a robust and adaptive approach to network security, integrating foundational principles with cutting-edge defensive mechanisms\cite{ref4}.

This paper reviews secured network infrastructure. The objective is to synthesize a cohesive understanding of the current network security landscape: its evolution, prevalent threats, and advanced mitigation strategies. We explore fundamental network components, including various network topologies (star, bus, ring, mesh) and the operational differences between Local Area Networks (LANs) and Wide Area Networks (WANs) \cite{ref4}. Understanding these building blocks is crucial for appreciating the complexities of securing modern digital environments.

Network security has dynamically evolved, marked by continuous innovation against emerging threats. Early packet filtering has progressed to sophisticated solutions like Stateful Inspection, Proxy, and Next-Generation Firewalls (NGFWs) \cite{ref5}. These advanced systems incorporate deep packet inspection, intrusion detection/prevention, and application awareness for multi-layered protection \cite{ref6}. Technologies such as Virtual Private Networks (VPNs) and Access Control Lists (ACLs) are critical for establishing secure communication channels and enforcing granular access policies \cite{ref7}.

The threat landscape involves a continuous arms race. This paper categorizes and discusses common network attacks, including Denial of Service (DoS/DDoS), Man-in-the-Middle (MitM), SQL Injection, Cross-Site Scripting (XSS), malware, insider threats, and zero-day exploits \cite{ref8}. Each attack exploits specific vulnerabilities, emphasizing the need for comprehensive security strategies. Network simulation tools, such as Packet Tracer and GNS3, are also examined as essential instruments for understanding network behavior, testing security configurations, and training cybersecurity professionals in controlled environments \cite{ref9}.

 this review offers a structured analysis of secured network infrastructure. Subsequent sections detail methodologies for securing networks, present key findings on defense mechanisms, discuss their implications, and outline future research directions. This paper aims to contribute to the ongoing discourse on cybersecurity by providing a holistic overview for practitioners and researchers alike.

