# Class of Service
Throughout the web portal, you will see certain screens have a class of service value that must be selected. The class of service can be thought of as a security feature. Currently, the following **screens** have this value:
- [Extensions](https://public.intellasoft.net/books/web-portal-dL9/page/overview-mCh)
- [Hunt Groups](https://public.intellasoft.net/books/web-portal-dL9/page/hunt-groups)
- [PhoneMap Groups](https://public.intellasoft.net/books/web-portal-dL9/page/phonemap-groups)
[](https://public.intellasoft.net/uploads/images/gallery/2024-07/bMQimage.png "Example of a class of service")
A Class of Service defines what numbers an associated group can call. It is possible to set up specific classes of service to handle specific numbers. By default, most Intellasoft installations will come with 4 default classes of service.
Additional options are available for creating **classes of services,** but you will need to contact your system administrator/IntellaSoft representative for options on configuring this. It is important to note that the class of service applies to calls that are being transferred from the extension/group that the class of service applies to. There are also options for blocking certain calls at the forefront without them gaining access to the phone system such as the IVR (Interactive Voice Response), live agents, individual extensions, etc.