ffap-ftp-default-user

ffap-ftp-default-user is a variable defined in `ffap.el'.
Its value is

"anonymous"

Documentation:
User name in FTP file names generated by `ffap-host-to-path'.
Note this name may be omitted if it equals the default
(either `efs-default-user' or `ange-ftp-default-user').

You can customize this variable.