Detection rules › Splunk
Unusual winlogon.exe Child Process (Sysmon)
Winlogon.exe is a core Windows process that manages secure user authentication events, such as logon, logoff, and screen locking. Expected child processes include LogonUI.exe for the login screen, FontDrvHost.exe for font rendering in secure sessions, Userinit.exe for initializing user settings, Consent.exe for User Account Control (UAC) prompts, and Sihost.exe for managing shell experience components like the Start menu and taskbar. This use case detects unexpected child processes spawned by winlogon.exe.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1547.004 Boot or Logon Autostart Execution: Winlogon Helper DLL |
| Privilege Escalation | T1547.004 Boot or Logon Autostart Execution: Winlogon Helper DLL |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
id: '39293.71042'
title: Unusual winlogon.exe Child Process
description: Winlogon.exe is a core Windows process that manages secure user authentication
events, such as logon, logoff, and screen locking. Expected child processes include
LogonUI.exe for the login screen, FontDrvHost.exe for font rendering in secure sessions,
Userinit.exe for initializing user settings, Consent.exe for User Account Control
(UAC) prompts, and Sihost.exe for managing shell experience components like the
Start menu and taskbar. This use case detects unexpected child processes spawned
by winlogon.exe.
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
TERM(winlogon) OR "winlogon.exe" | regex parent_process_name="(?i)winlogon\.exe"|
regex process_path!="(?i)\x5cWindows\x5cSystem32\x5c(AtBroker|LogonUI|dwm|fontdrvhost|userinit|consent|sihost)\.exe"
| table _time, host, user, process, process_*, parent_* | bin span=1s | stats values(*)
as * by _time, host '
techniques:
- persistence:boot or logon autostart execution:winlogon helper dll
- privilege-escalation:boot or logon autostart execution:winlogon helper dll
technique_id:
- T1547.004
data_category:
- Windows Sysmon
references:
- https://github.com/tykawaii98/CVE-2024-30088
- https://securityonline.info/poc-exploit-published-for-windows-kernel-elevation-of-privilege-vulnerability-cve-2024-30088/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<") TERM(winlogon) OR "winlogon.exe"
Stage 2: regex
| regex parent_process_name="(?i)winlogon\.exe"
Stage 3: regex
| regex process_path!="(?i)\x5cWindows\x5cSystem32\x5c(AtBroker|LogonUI|dwm|fontdrvhost|userinit|consent|sihost)\.exe"
Stage 4: table
| table _time, host, user, process, process_*, parent_*
Stage 5: bucket
| bin span=1s
Stage 6: stats
| stats values(*) as * by _time, host
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
process_path | regex_match | "(?i)\x5cWindows\x5cSystem32\x5c(AtBroker|LogonUI|dwm|fontdrvhost|userinit|consent|sihost).exe" |
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
EventCode | eq |
|
parent_process_name | regex_match |
|
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>1<" |
| 1 | TERM |
| 1 | winlogon |
| 1 | "winlogon.exe" |