Detection rules › Splunk
Suspicious Parent Process for spoolsv.exe (Windows Event Log)
This use case detects when the Windows print spooler process (spoolsv.exe) is executed as a child from an unexpected parent process. This can indicate process injection/hollowing, masquerading, or other suspicious activity. The expected parent process for spoolsv.exe is services.exe.
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 |
|---|---|---|
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
id: '16165.24269'
title: Suspicious Parent Process for spoolsv.exe
description: This use case detects when the Windows print spooler process (spoolsv.exe)
is executed as a child from an unexpected parent process. This can indicate process
injection/hollowing, masquerading, or other suspicious activity. The expected parent
process for spoolsv.exe is services.exe.
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
"<EventID>4688<" OR Type=Process) "spoolsv.exe" | regex process_path="(?i)\x5csystem32\x5cspoolsv\.exe"|
regex parent_process_name!="(?i)services\.exe|\%14\!S\!"| where isnotnull(parent_process_name)
and not match(parent_process_name, "^-$") | table _time, host, user process, process_*,
parent_process_name, parent_process_* | bin span=1s | stats values(*) as * by _time,
host '
techniques:
- defense-evasion:masquerading:masquerade task or service
- defense-evasion:process injection
technique_id:
- T1036.004
- T1055
data_category:
- Windows event logs
references:
- https://andreafortuna.org/2017/06/15/standard-windows-processes-a-brief-reference/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) "spoolsv.exe"
Stage 2: regex
| regex process_path="(?i)\x5csystem32\x5cspoolsv\.exe"
Stage 3: regex
| regex parent_process_name!="(?i)services\.exe|\%14\!S\!"
Stage 4: where
| where isnotnull(parent_process_name) and not match(parent_process_name, "^-$")
Stage 5: table
| table _time, host, user process, process_*, parent_process_name, parent_process_*
Stage 6: bucket
| bin span=1s
Stage 7: stats
| stats values(*) as * by _time, host
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
parent_process_name | regex_match | "(?i)services.exe, \%14\NOT S\!" |
parent_process_name | match | "^-$" |
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 | is_not_null | |
process_path | 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>4688<" |
| 1 | "spoolsv.exe" |