The default product configuration has a simple chain with one member. This is an instance of the alfrescoNtlm subsystem type with and ID of alfrescoNtlm1.
This is expressed in the built-in defaults in the repository.properties file as:
authentication.chain=alfrescoNtlm1:alfrescoNtlm
You can configure the properties of alfrescoNtlm1 using the alfresco-global.properties file.