Definition
RADIUS stands for Remote Authentication Dial-In User Service and is a networking protocol that provides centralized authentication, authorization, and accounting (AAA) management for users connecting to a network. It operates using a client server model where network access devices act as RADIUS clients, forwarding user authentication requests to a central RADIUS server. This system is crucial for enforcing consistent security policies and managing access across various network resources, from Wi-Fi hotspots to VPN connections. For instance, when you connect to a corporate Wi-Fi network, your credentials are often sent via RADIUS to verify your identity and permissions. Unlike simpler authentication methods that might authenticate users locally on each device, RADIUS centralizes this process, simplifying administration and enhancing security. You will encounter RADIUS concepts on CompTIA Security+, CySA+, and CISSP certification exams.