Detection: Windows Cloud Files Filter Log Created by Non-System Process

Updated Date: 2026-05-01 ID: 2e0042b9-8a75-49ca-b3a2-948f04b752bf Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

Detects a non-system process causing creation of CldFlt0.etl under C:\Windows\System32\LogFiles\CloudFiles. This path is initialised by the CldFlt driver when a process calls CfRegisterSyncRoot() or CfConnectSyncRoot(). In the RedSun exploit this is a side-effect of the DoCloudStuff() function that registers a fake sync provider to create the cloud-tagged bait file. Legitimate cloud providers (OneDrive etc.) register sync roots from SYSTEM-level service processes, not from user-context executables.

Search

 1`sysmon`
 2EventCode=11
 3TargetFilename = "*\\Windows\\System32\\LogFiles\\CloudFiles\\*"
 4NOT Image IN (
 5    "*:\\Windows\\System32*",
 6    "*:\\Windows\\SysWOW64*",
 7    "*:\\Program Files\\WindowsApps\\*"
 8)
 9
10| stats count min(_time) as firstTime
11              max(_time) as lastTime
12  by action dest file_name file_path Image process_guid
13     process_id user_id vendor_product
14
15| `security_content_ctime(firstTime)`
16
17| `security_content_ctime(lastTime)`
18
19| `windows_cloud_files_filter_log_created_by_non_system_process_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 11	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_cloud_files_filter_log_created_by_non_system_process_filter	`search *`

windows_cloud_files_filter_log_created_by_non_system_process_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1068	Exploitation for Privilege Escalation	Privilege Escalation

Exploitation

DE.CM

CIS 10

CVE

CVE-2026-33825

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	No

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

No false positives have been identified at this time.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
Non-System process $Image$ created a cloud files filter $file_name$ on host $dest$	dest	system	50

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1