Detection rules › Splunk
Suspicious Child Process for lsass.exe (Sysmon)
This use case detects when the Local Security Authority Subsystem Service (lsass.exe) spawns a child process. This can indicate process injection/hollowing, masquerading, or other suspicious activity. Normal activity for lsass.exe does not typically include spawning child processes, with the exception of EFS (Encrypting File System)
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Privilege Escalation | T1055 Process Injection |
| Stealth | T1036.004 Masquerading: Masquerade Task or Service, T1055 Process Injection |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
id: '19108.32982'
title: Suspicious Child Process for lsass.exe
description: 'This use case detects when the Local Security Authority Subsystem Service
(lsass.exe) spawns a child process. This can indicate process injection/hollowing,
masquerading, or other suspicious activity. Normal activity for lsass.exe does not
typically include spawning child processes, with the exception of EFS (Encrypting
File System). Atomics T1134.002 Test #1'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
TERM(lsass) OR "lsass.exe" | regex parent_process_name="(?i)lsass\.exe" | table
_time, host, user process, process_*, parent_process_name, parent_process_* | bin
span=1s | stats values(*) as * by _time, host '
techniques:
- defense-evasion:masquerading:masquerade task or service
- defense-evasion:process injection
technique_id:
- T1036.004
- T1055
data_category:
- Windows Sysmon
references:
- https://andreafortuna.org/2017/06/15/standard-windows-processes-a-brief-reference/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<") TERM(lsass) OR "lsass.exe"
Stage 2: regex
| regex parent_process_name="(?i)lsass\.exe"
Stage 3: table
| table _time, host, user process, process_*, parent_process_name, parent_process_*
Stage 4: bucket
| bin span=1s
Stage 5: stats
| stats values(*) as * by _time, host
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 | lsass |
| 1 | "lsass.exe" |