I've got a normal app to connect to the minifilter communication port using FilterConnectCommunicationPort. First problem is that fltuser.h not found. Apparently It's not part of the $(VCInstallDir)include items, not part of the $(WindowsSDKDir)\include folder. Searching I find it in "\program files (x86)\windows kits\8.0\include\um" and "\program files (x86)\windows kits\8.1\include\um" as well as in various items under \WinDDK (3790.1830\inc\ifs\w2k, 3790.1830\inc\ifs\wnet, 3790.1830\inc\ifs\wxp, and 7600.16385.1\inc\ddk ). So I just went ahead and added an include directory for the project (VS2008) to be \WinDDK\7600.16385.1\inc\ddk and now the compile works, but link fails. What is the .lib to link to? How is the user mode side of things intended to be used?