Hi
Well... i dont know much about the connection string, but i can tell you how i solved something simular to this.
To make sure that one specific asp file got limited access, put it in another folder and put OS Security on the folder.
Result of this is that the user trying to access the asp file within that folder, will have to authenticate to access it.
This is controlled on OS Security level (users, groups etc.etc..)
Hope it helped..
Mirador...