Once started it creates additional paging files with configuration data from HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management,[1] the environment variables located at the registry entry HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment, and DOS device mappings (e.g. CON:, NUL:, AUX:, COM1:, COM2:, COM3:, COM4:, PRN:, LPT1:, LPT2:, LPT3:, and drive letters) listed at the HKLM\System\CurrentControlSet\Control\Session Manager\DOS Devices registry key.
[5] Once the session is configured, the Session Manager Subsystem starts Winlogon (Windows Logon Application), which is responsible for handling interactive logons to a Windows system, either local or remote.
[5] After the boot process is finished, the program resides in memory and can be seen running in the Windows Task Manager.
If the processes do not end in an expected fashion, smss.exe may hang the system, or a bugcheck will occur.
In some versions of Windows, by using special tools, the critical process status on smss.exe can be removed, after that, it can be terminated without a bluescreen, but any functions that use smss.exe stop working until the next reboot.