This warning appears when you choose to use the Basic authentication method. With basic authentication, the user's Web browser transmits Windows account user names and passwords across the network in plaintext. Malicious users can then intercept this information. You can use Basic authentication and still protect account information using Secure Sockets Layer (SSL) encryption. To enable SSL, you must first install a server certificate.
Click to implement the authentication option selected and continue with the security configuration.
Click to cancel the selection of the authentication option and return to the previous dialog box.
To learn more about user authentication, encryption, and Secure Sockets Layer, see the IIS 6.0 online documentation on the Microsoft Windows Server TechCenter.