What is a RADIUS server?

RADIUS stands for Remote Authentication Dial-In User Service and is a networking protocol that provides centralised authentication, authorisation and accounting management for users to connect to and use a service. RADIUS does not encrypt any of the attributes passed between client and server, except passwords. A RADIUS server therefore provides a relatively simple way to connect and authenticate a device that is not part of a Microsoft Active Directory domain. RADIUS can be used with other security mechanisms including virtual private networks (VPNs) and supports multi-factor authentication (MFA) and the Extensible Authentication Protocol (EAP) used in local area networks (LANs).