You can use the the <authentication>, <authorization> and <location&tg; elements to restrict permissions on specific pages/folders to certain users. In intranet scenarios, you'll probably use Windows authentication:
<system.web> <authentication mode="Windows" /> <deny users="?" /> <allow users="*" /> </system.web>
Here we allow all non-anonymous users to use the site. Then you can add any number of <location> elements to specify more granular behavior:
<location path="SecurePages/Secure.aspx"> <system.web> <authorization> <deny users="*" /> <allow users="MYDOMAINJohn" /> </authorization> </system.web> </location>
Here we restricted the Secure.aspx page to John, user of the Windows domain MYDOMAIN. IIS should be configured accordingly to allow either Windows integrated (most secure but users must belong to the domain) or basic/digest authentication modes. Definitely, anomymous should NOT be the only option, because nobody will ever be prompted for credentials.
This was first published in September 2003