An advanced local procedure call (ALPC) is an interprocess communication facility for high-speed message passing. It is not directly available through the Windows API; it is an internal mechanism available only to Windows operating system components. Here are some examples of where ALPCs are used:
Windows applications that use remote procedure calls (RPCs), a documented API, indirectly use ALPCs when they specify local-RPC, a form of RPC used to communicate between processes on the same system.
A few Windows APIs result in sending messages to the Windows subsystem process.
Winlogon uses ALPCs to communicate with the local security authentication server process, LSASS.
The security reference monitor (an executive ...