IIS 6.0 supports multiple methods of authentication so that you can confirm the identity of everyone who requests access to your Web sites. For example, IIS 6.0 supports the following authentication methods:
Anonymous authentication. This authentication method allows everyone access to your Web sites, without asking for a user name or password.
Basic authentication. This authentication method prompts the user for a user name and a password, which are sent unencrypted over the network.
Digest authentication. This authentication method operates much like Basic authentication, except that passwords are sent as a hash value. Digest authentication is available only on domains with domain controllers running Windows server operating systems. ...