This allows IIS to define the security context that the request runs under. mod_fastcgi under Apache does not currently support this feature (03 / 17 / 2002) Set to 1 if running under IIS.
FastCGI under IIS (on WINNT based OS) supports the ability to impersonate security tokens of the calling client. This allows IIS to define the security context that the request runs under. mod_fastcgi under Apache does not currently support this feature (03/17/2002) Set to 1 if running under IIS. Default is zero.