samba - Mar 1998 - Password Cacheing for User-Level security under NT4 (SP3)

Is there some mechanism within either Samba (1.9.17p5) or NT4 that
would allow system passwords to be shared when the samba security
option=user?  I've got a situation where a newly booted (or just logged off)
NT4 system can be logged into a then the user can jump right into the
samba server without being prompted for a username or password!

This scares me just a bit.. Now, after perusing the logs for a bit, I can
see
that it is rejecting other users that do NOT have a corresponding Unix
account, but I'm still wondering WHY it is doing this!  When it does this
for a valid user, there is nothing in the logs stating that it is looking
for a
password!  This is happening on a Solaris 2.6 machine which is otherwise
working fine!

-- Rick