security manager for one object (or thread) only

[Thomas Jollans]

I use user-written classes in my app and I would like to implement a bit
of security. But there are a few problems:

- I want to configure the security for each class seperately
- My main prog must have access to the hard drive, but the user-written
classes usually shouldn't.

Is this possible? can I make a one-object-only security manager (or
something similar)? or can i ask who tried to do something "bad" (needs
a security manager)?

thomas