smss.exe
Sources: 300M+ executions observed in the wild.
Summary
Windows Session Manager Subsystem - first user-mode process started by the kernel during boot. Creates sessions, launches csrss.exe and winlogon.exe.
smss.exe is the 252nd most commonly executed Windows program in EchoTrail's dataset, observed 50,971 times across enterprise environments. It typically runs from C:\Windows\System32 and it is most often launched by smss.exe.
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Behavior
Top Paths
- C:\Windows\System32100%
Top Hashes (SHA256)
- 4ce6cb811547ed1d0b29d86fa9ece63e5fb5dcfe680ebe1abc269a2b80b0999324.67%
- f6066162e9e4f279d2d5f0c207c209ae8c2b13fc7555186f32c7e8ce49eb52a212.21%
- fc8ef5704c871187ae4945000db3d3758e8b867e90f8e530b0f12c6438d17d358.57%
- 7cfc64ff84039e354279defc4eb81d1afd4bfcc8f336b4ec699374e0dd8aa5d87.55%
- 56afe5133fdc5806ec6b19436f7b55f1499cfc94619740c171424fbcf7808fd36.72%
- 5f48638e3397204c2c63d7b76d025d62302d0e45fc5055c0a692b0bbc7e6b3375.3%
- 741c2f38a26381f2e6f439d4ff5b2759e66343303500a8509dba93d09a908f264.58%
- 3601ce0df53f7b14132cbd435c073ce009694f4b73ea5fff46b93a7413daf8e24.28%
- a15df33f7b666bc79a2fe9864442623aaea393552591a4ab1f3a7cb29cf40dae4.02%
- f77972f1e5ff7993e2cd206d3d2b8f42ea9807f1384d0a8ec90f08a6f075b7512.08%
Process Ancestry
Top Parents
- smss.exe86.28%
Top Children
- csrss.exe30.09%
- smss.exe28.93%
- winlogon.exe22.9%
- autochk.exe8.58%
- wininit.exe7.88%
- SophosNA.exe1.49%
- wpbbin.exe0.08%
- LogonUI.exe0.01%
- poqexec.exe0.01%
- conhost.exe<0.01%
Security Analysis
What does smss.exe normally do?
Runs as Session 0 from %SystemRoot%\System32\smss.exe. Creates csrss.exe and wininit.exe (Session 0) or csrss.exe and winlogon.exe (Session 1+). Only one master instance persists after boot.
When is smss.exe suspicious?
Multiple persistent instances. Running from any path other than System32. Parent other than System (PID 4). Running in an interactive session.
How do attackers abuse smss.exe?
Malware masquerades as smss.exe by placing executables with the same name in writable directories. Real smss.exe should never have a user-visible window.
Detection guidance
Validate single master instance with parent PID 4. Verify path is exactly %SystemRoot%\System32\smss.exe. Any deviation is high-confidence malicious.
False positive notes
Temporary child smss.exe instances during session creation are normal but should exit quickly.
Related Processes
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