int main() HMODULE hNtdll = GetModuleHandleA("ntdll.dll"); pNtOpenWnfState NtOpenWnfState = (pNtOpenWnfState)GetProcAddress(hNtdll, "NtOpenWnfState"); pNtQueryWnfStateData NtQueryWnfStateData = (pNtQueryWnfStateData)GetProcAddress(hNtdll, "NtQueryWnfStateData");
Here’s where NtQueryWnfStateData shines : 3.1 Real-time, Low-Overhead State Reading WNF updates are kernel-pushed. Polling a registry key or waiting for a broadcast message is slow and wasteful. NtQueryWnfStateData reads the current state directly from the kernel’s WNF database. 3.2 Access to Hidden System States Many system states are only exposed via WNF, not through public APIs. For example, the internal “Game Mode” state, specific power throttling modes, or the Windows Update orchestrator status can be read via WNF but not via GetSystemPowerStatus . 3.3 No Admin Rights Needed (Often) Unlike reading kernel memory directly or loading a driver, many WNF states are readable from a medium integrity process (standard user). This makes NtQueryWnfStateData a powerful tool for non-admin diagnostic tools. 3.4 Faster than WMI or ETW WMI queries are notoriously slow. ETW requires enabling providers, collecting traces, and parsing events. NtQueryWnfStateData is a simple synchronous syscall – often completing in < 1 microsecond. Part 4: How to Find WNF State Names To use NtQueryWnfStateData , you need a StateHandle or a StateName . WNF State Names are 128-bit values. Some are publicly known from leaked symbols or reverse engineering. Examples: ntquerywnfstatedata ntdlldll better
However, with great power comes great responsibility. Because this function is undocumented, you must be prepared for maintenance headaches and potential version incompatibilities. Yet, for security researchers, performance tooling developers, and Windows internals enthusiasts, adding NtQueryWnfStateData to your toolkit is undeniably a step toward a understanding of the operating system's inner workings. int main() HMODULE hNtdll = GetModuleHandleA("ntdll
NTSTATUS NtQueryWnfStateData( HANDLE StateHandle, VOID* UnknownBuffer1, // often a WNF change stamp buffer ULONG UnknownSize, VOID* Buffer, // output data ULONG BufferSize, ULONG* ReturnLength ); Its purpose: retrieve the current data associated with a given WNF state name. You might ask: Why not just use the documented GetSystemMetrics or RegNotifyChangeKeyValue ? This makes NtQueryWnfStateData a powerful tool for non-admin
WNF is an internal, kernel-mode notification system introduced in Windows 8 and heavily utilized in Windows 10 and 11. It allows different components of the OS (drivers, services, user-mode apps) to publish and subscribe to state changes without needing a full RPC or COM infrastructure.