you can use the APP to strip Referer header. The header is attached by MSHTML in HttpNegotiate::BeginningTransaction.
see also
http://msdn.microsoft.com/workshop/networking/pluggable/pluggable.asp
http://support.microsoft.com/?id=kb;en-us;303740
http://home.nyc.rr.com/itandetnik/PassthruAPP.zip