Multiple Different FEs - Common BE security

[David Mulholland]

I maintain almost two dozen different databases for different departments.
There is a single common BE database that is shared by most. Is there a way
to set a password on that common BE and use code to pass the password from
the FE to the BE without any user intervention? I want to secure the common
BE from being linked to by any databases outside my control. I don't use
user-level permissions right now, due to the sheer number of users/groups I'd
have to create.

Any ideas/thoughts/comments??