Controlling Access to an Extranet
http://www.intranetjournal.com/articles/200105/ex_05_16_01a.html

Bloomberg, Jason
Intranet Journal

Abstract:

The only real difference today among an extranet, an intranet, and a public Web site is how and when users can access the site. Intranets are often on private networks, and extranets are occasionally, as well; but today's robust access-control mechanisms make private networks less and less essential to providing secure access to either an extranet or an intranet. On the other hand, password-protecting portions of a public Web site is becoming more and more common, and isn't a password-protected Web site the same thing as an extranet?