User login with LDAP authentication even though account is not created in Moodle

Dear All,

We are using LDAP Server for authentication.  User must have their account created in Moodle, then they can login to Moodle with their existing active directory username and password.

But, now any active directory user also can login to  Moodle, even though the account has not create. Because, Moodle will allow them to create the new account. 

Can we make moodle to check if the account has not created in Moodle, so they cann't login.  Do we miss any setting?

Appreciate for the help.

Thanks,

Yulstar