Detection rules › Splunk
Rundll32 Spawned by Disk Cleanup (Windows Event Log)
The Windows Disk Cleanup utility is a legacy tool designed to delete cache and temporary files to improve system performance and free up hard disk space. It is possible to abuse the utility to establish persistence by executing arbitrary code when Disk Cleanup is initiated via COM hijacking. This use case detects rundll32.exe processes launched by CleanMgr.exe (Disk Cleanup binary), indicating potential COM hijacking has taken place
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1546.015 Event Triggered Execution: Component Object Model Hijacking |
| Privilege Escalation | T1546.015 Event Triggered Execution: Component Object Model Hijacking |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
id: '28613.52077'
title: Rundll32 Spawned by Disk Cleanup
description: The Windows Disk Cleanup utility is a legacy tool designed to delete
cache and temporary files to improve system performance and free up hard disk space.
It is possible to abuse the utility to establish persistence by executing arbitrary
code when Disk Cleanup is initiated via COM hijacking. This use case detects rundll32.exe
processes launched by CleanMgr.exe (Disk Cleanup binary), indicating potential COM
hijacking has taken place. Living Off the Land Binary and Scripts (LOLBAS) (LOLBIN)
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
"<EventID>4688<" OR Type=Process) "cleanmgr" "rundll32" | where match(parent_process_name,
"(?i)cleanmgr\.exe") and match(process_name, "(?i)rundll32\.exe") | table _time,
host, user, parent_*, process, process_* | bin span=1s | stats values(*) as * by
_time, host '
techniques:
- persistence:event triggered execution:component object model hijacking
technique_id:
- T1546.015
data_category:
- Windows event logs
references:
- https://pentestlab.blog/2024/01/29/persistence-disk-clean-up/
- https://cocomelonc.github.io/persistence/2022/11/16/malware-pers-19.html
- https://www.hexacorn.com/blog/2018/09/02/beyond-good-ol-run-key-part-86/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) "cleanmgr" "rundll32"
Stage 2: where
| where match(parent_process_name, "(?i)cleanmgr\.exe") and match(process_name, "(?i)rundll32\.exe")
Stage 3: table
| table _time, host, user, parent_*, process, 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 | match |
|
process_name | 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 | "cleanmgr" |
| 1 | "rundll32" |