Does DNN have the ability to support restriction of user logins to one single active session?  I have a subscription based website and I want to limit the ability of people sharing their usernames and passwords with friends.  I realize this isn't a foolproof solution, but if I could restrict a DNN user to only having one active login session I would be happier.  Any ideas on how to implement this with either a core change, a module or some other solution?

Create custom login module base on signin.ascx (located at folder admin/security).

Modify the cmdLogin click event handler. Basicaly you just need to check wether the user already exist in the cache or not (When login usually user info will be stored in the cache and when logout the cache will be cleared automaticaly ).

Dim cacheKey As String = String.Format("UserInfo|{0}|{1}", portalId, txtUsername.Text)

Dim objObject As UserInfo = DirectCast(DataCache.GetCache(cacheKey), UserInfo)

Can the functionality of the Users Online module be expanded to do this?  I have also wondered about this type of solution.

Carlos