User Access Permission Replaced by Domain Controller User Permission Policy

Dear all and support team, 

I have a case where my PowerBI report server is accessed by unauthorized user. After checking the log files and do some testing, I found that the user have an ADMIN DOMAIN role on domain controller and further checking shows all user with same role (admin domain) have a permission to access all reports whereas I didn't assign the user on user permission/authentication configuration. Is it possible to apply only configuration from PowerBI report server rather than domain controller? or is there any specific configuration/setting that we need to review & adjust? 

Any support will greatly appreciated, 

thank you

rachmat