ASP.NET with IIS, can authenticate user credentials such as names and passwords using any of the following authentication methods:

•Windows: Basic, digest, or Integrated Windows Authentication (NTLM or Kerberos).
•Microsoft Passport authentication
•Forms authentication
•Client Certificate authentication

ASP.NET has two security functions i.e Authentication and Authorization.

Authentication  – Helps to verify the user. Tells who the user is ?
Authorization – Limits access rights by granting or denying specific permissions to an authenticated identity