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Windows Cloud Files Filter Log Created by Non-System Process

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…

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.

Detection logic

Detection requirements

Platform
ContainersLinuxmacOSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
sysmon_eventid_11

Known benign triggers

  • No false positives have been identified at this time.

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