Detection rules › Splunk
Office Spawns Suspicious Child Process (Windows Event Log)
This use case attempts to identify suspicious child processes spawned from a Microsoft Office application
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Execution | T1204.002 User Execution: Malicious File |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
id: '19686.34350'
title: Office Spawns Suspicious Child Process
description: 'This use case attempts to identify suspicious child processes spawned
from a Microsoft Office application -- Threat Actor Association: RomCom (Storm-0978)
-- Vulnerability Association: CVE-2023-36884'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
"<EventID>4688<" OR Type=Process) (powershell.exe OR pwsh.exe OR cmd.exe OR mshta.exe
OR wscript.exe OR cscript.exe OR regsvr32.exe OR rundll32.exe OR taskkill.exe OR
csc.exe OR calc.exe OR control.exe) ((Microsoft OR Office) OR WINWORD.EXE OR EXCEL.EXE
OR POWERPNT.EXE OR MSACCESS.EXE OR OUTLOOK.EXE OR VISIO.EXE OR WINPROJ.EXE OR ONENOTE.EXE
OR GRAPH.EXE OR MSPub.EXE OR wordpad.exe) | regex process_name="(?i)(powershell|pwsh|cmd|mshta|wscript|cscript|regsvr32|rundll32|taskkill|csc|calc|control)\.exe"|
regex parent_process_path="(?i)Microsoft\sOffice|winword|excel|powerpnt|msaccess|outlook|visio|winproj|onenote|graph|mspub|wordpad"
| table _time, host, user process, parent_*, process_*, signature_id | bin span=1s
| stats values(*) as * by _time, host, parent_process_name | where match(parent_process_path,"(?i)(Microsoft
Office)|(WINWORD\.EXE)|(EXCEL\.EXE)|(POWERPNT\.EXE)|(MSACCESS\.EXE)|(OUTLOOK\.EXE)|(ONENOTE\.EXE)|(VISIO\.EXE)|(WINPROJ\.EXE)|(GRAPH\.exe)|(MSPub\.exe)|(WINPROJ.EXE\.exe)|(wordpad\.exe)") '
techniques:
- execution:user execution:malicious file
technique_id:
- T1204.002
data_category:
- Windows event logs
references:
- https://fourcore.io/blogs/cve-2023-36884-ms-office-zero-day-vulnerability
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) (powershell.exe OR pwsh.exe OR cmd.exe OR mshta.exe OR wscript.exe OR cscript.exe OR regsvr32.exe OR rundll32.exe OR taskkill.exe OR csc.exe OR calc.exe OR control.exe) ((Microsoft OR Office) OR WINWORD.EXE OR EXCEL.EXE OR POWERPNT.EXE OR MSACCESS.EXE OR OUTLOOK.EXE OR VISIO.EXE OR WINPROJ.EXE OR ONENOTE.EXE OR GRAPH.EXE OR MSPub.EXE OR wordpad.exe)
Stage 2: regex
| regex process_name="(?i)(powershell|pwsh|cmd|mshta|wscript|cscript|regsvr32|rundll32|taskkill|csc|calc|control)\.exe"
Stage 3: regex
| regex parent_process_path="(?i)Microsoft\sOffice|winword|excel|powerpnt|msaccess|outlook|visio|winproj|onenote|graph|mspub|wordpad"
Stage 4: table
| table _time, host, user process, parent_*, process_*, signature_id
Stage 5: bucket
| bin span=1s
Stage 6: stats
| stats values(*) as * by _time, host, parent_process_name
Stage 7: where
| where match(parent_process_path,"(?i)(Microsoft Office)|(WINWORD\.EXE)|(EXCEL\.EXE)|(POWERPNT\.EXE)|(MSACCESS\.EXE)|(OUTLOOK\.EXE)|(ONENOTE\.EXE)|(VISIO\.EXE)|(WINPROJ\.EXE)|(GRAPH\.exe)|(MSPub\.exe)|(WINPROJ.EXE\.exe)|(wordpad\.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_path | match |
|
parent_process_path | regex_match |
|
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>4688<" |
| 1 | powershell.exe |
| 1 | pwsh.exe |
| 1 | cmd.exe |
| 1 | mshta.exe |
| 1 | wscript.exe |
| 1 | cscript.exe |
| 1 | regsvr32.exe |
| 1 | rundll32.exe |
| 1 | taskkill.exe |
| 1 | csc.exe |
| 1 | calc.exe |
| 1 | control.exe |
| 1 | Microsoft |
| 1 | Office |
| 1 | WINWORD.EXE |
| 1 | EXCEL.EXE |
| 1 | POWERPNT.EXE |
| 1 | MSACCESS.EXE |
| 1 | OUTLOOK.EXE |
| 1 | VISIO.EXE |
| 1 | WINPROJ.EXE |
| 1 | ONENOTE.EXE |
| 1 | GRAPH.EXE |
| 1 | MSPub.EXE |
| 1 | wordpad.exe |