InformationForms-based authentication can pass credentials across the network in clear text. It is therefore imperative that the traffic between client and server be encrypted using SSL, especially in cases where the site is publicly accessible. It is recommended that communications with any portion of a site using Forms Authentication be encrypted using SSL.
Requiring SSL for Forms Authentication will protect the confidentiality of credentials during the login process, helping mitigate the risk of stolen user information.
Solution 1. Open IIS Manager and navigate to the appropriate tier
2. In Features View, double-click Authentication
3. On the Authentication page, select Forms Authentication
4. In the Actions pane, click Edit
5. Check the Requires SSL checkbox in the cookie settings section, click OK