<Global Settings>
Http Configuration → Change Password (available from firmware V650Bxx, a change would require the http_user and http_pass credentials)
<http_basic_user>VALIDVALUE</http_basic_user>
It defines the HTTP username for the lower-level user (starting from firmware V610Bxx), together with http_basic_pass it can be configured to grant access to some of the pages on the web interface (NOTICE: the higher level access will continue to be granted by http_user and http_pass).
e.g. admin
Engineer (on firmware V610Bxx)
User (starting from firmware B650Bxx)