userinit.exe
Sources: 300M+ executions observed in the wild.
Summary
Windows Userinit Logon Application - runs logon scripts and launches explorer.exe during user logon. Executes briefly then exits.
userinit.exe is the 326th most commonly executed Windows program in EchoTrail's dataset, observed 27,711 times across enterprise environments. It typically runs from C:\Windows\System32 and it is most often launched by winlogon.exe.
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Behavior
Top Paths
- C:\Windows\System32100%
Top Hashes (SHA256)
- df141a362d88dec14bb655f4a1757769e0adb3251b4571167a1227cba6274adb25.46%
- 7065057320320c99d0749f1dedcbea2e5b540404497244eb5f92ded38646f21d12.92%
- b5170d0e86b93d83c67636fe2c1207139cfcbc9114bbfd74d127cddcbd8fa11412.02%
- eda7ee39d4db8142a1e0788e205e80ae798035d60273e74981e09e98c8d0e7409.33%
- 89dd6946608b000161858ccd5af2c3d5a078856def17272795bd5cbe053b0ea08.36%
- 016b8f2067d9a18b5d14f33c8ed98d61ea7c63fd53af5b25b117e2e982e5b7807.83%
- 1fe7f7c59ec7eaa276739fa85f7dda6136d81184e0aeb385b6ac9feaaa8c43945.06%
- cfc6a18fc8fe7447ecd491345a32f0f10208f114b70a0e9d1cd72f6070d5b36f3.16%
- 03c963391d522a764136008a878369c07fcdf05083274a8a9f27348a14e13d552.68%
- 11c194d9adce90027272c627d7fbf3ba5025ff0f7b26a8333f764e11e1382cf92.44%
Process Ancestry
Top Grandparents
- smss.exe97.97%
- svchost.exe0.82%
- winlogon.exe0.8%
- nvvsvc.exe0.08%
- fontdrvhost.exe0.07%
- dwm.exe0.06%
- nvwmi64.exe0.05%
- WUDFHost.exe0.05%
- LogonUI.exe0.03%
- hmpalert.exe0.01%
Top Parents
- winlogon.exe99.07%
- smss.exe<0.01%
Top Children
- explorer.exe95.74%
- cmd.exe3.64%
- rdpinit.exe0.52%
Security Analysis
What does userinit.exe normally do?
Runs from %SystemRoot%\System32\userinit.exe. Launched by winlogon.exe during logon. Spawns explorer.exe and any logon scripts, then exits quickly.
When is userinit.exe suspicious?
Persistent execution (should exit quickly after logon). Running from non-System32 path. Parent other than winlogon.exe. Spawning processes other than explorer.exe or logon scripts.
How do attackers abuse userinit.exe?
Registry key HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit can be modified to point to malware instead of or in addition to userinit.exe. Malware persistence technique.
Detection guidance
Monitor the Userinit registry value for modifications. Alert if userinit.exe runs from unexpected path or has unexpected parent. Long-running userinit.exe is suspicious.
False positive notes
Group Policy logon scripts may cause userinit.exe to spawn various interpreters (cmd.exe, powershell.exe, cscript.exe).
Related Processes
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