Windows Cloud Files Filter Log Created by Non-System Process

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.

Query · spl

`sysmon`
EventCode=11
TargetFilename = "*\\Windows\\System32\\LogFiles\\CloudFiles\\*"
NOT Image IN (
    "*:\\Windows\\System32*",
    "*:\\Windows\\SysWOW64*",
    "*:\\Program Files\\WindowsApps\\*"
)
| stats count min(_time) as firstTime
              max(_time) as lastTime
  by action dest file_name file_path Image process_guid
     process_id user_id vendor_product
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `windows_cloud_files_filter_log_created_by_non_system_process_filter`

Implementation guide

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.

Analyst notes

Known false positives: No false positives have been identified at this time.

Raw source Windows Cloud Files Filter Log Created by Non-System Process · SPL
Esc
Published by splunk/security_content ↗, licensed under Apache 2.0 ↗. Reproduced here unmodified. 
name: Windows Cloud Files Filter Log Created by Non-System Process
id: 2e0042b9-8a75-49ca-b3a2-948f04b752bf
version: 1
creation_date: '2026-05-01'
modification_date: '2026-05-01'
author: Raven Tait, Splunk
status: production
type: TTP
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.
data_source:
    - Sysmon EventID 11
search: |-
    `sysmon`
    EventCode=11
    TargetFilename = "*\\Windows\\System32\\LogFiles\\CloudFiles\\*"
    NOT Image IN (
        "*:\\Windows\\System32*",
        "*:\\Windows\\SysWOW64*",
        "*:\\Program Files\\WindowsApps\\*"
    )
    | stats count min(_time) as firstTime
                  max(_time) as lastTime
      by action dest file_name file_path Image process_guid
         process_id user_id vendor_product
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_cloud_files_filter_log_created_by_non_system_process_filter`
how_to_implement: 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.
references:
    - https://github.com/Nightmare-Eclipse/RedSun
    - https://www.huntress.com/blog/nightmare-eclipse-intrusion
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: Non-System process $Image$ created a cloud files filter $file_name$ on host $dest$
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - RedSun
    - Windows Privilege Escalation
asset_type: Endpoint
cve:
    - CVE-2026-33825
mitre_attack_id:
    - T1068
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1068/redsun/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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