Session Manager Subsystem

Session Manager Subsystem, or smss.exe, is a component of the Microsoft Windows NT family of operating systems, starting in Windows NT 3.1. It is executed during the startup process of those operating systems. At this time it:

After the boot process is finished, the program resides in memory and can be seen running in the Windows Task Manager. It then waits for either winlogon.exe or csrss.exe to end else Windows will shut down. If the processes do not end in an expected fashion, smss.exe may hang the system.