Windows DLL sideloading: CCleanerDU.dll loaded outside CCleaner binaries

Alerts when CCleanerDU.dll is loaded, but the loading image is not CCleaner executables in standard install paths.

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windows-dll-sideloading-ccleanerdu-dll-loaded-outside-ccleaner-binaries-1fbc0671

title: "Windows DLL sideloading: CCleanerDU.dll loaded outside CCleaner binaries"
id: f167bf79-c580-4082-b77d-b85cd02c0be6
status: test
description: This rule flags instances where Windows loads a DLL named "CCleanerDU.dll" when it is not associated with loading from the expected CCleaner installation executables. DLL sideloading is a common technique to execute attacker-controlled code by forcing a process to load a malicious or unintended DLL. The detection relies on image-load telemetry that records the loaded DLL path and the parent/executing image path (e.g., CCleaner.exe or CCleaner64.exe) to exclude likely legitimate loads.
references:
  - https://lab52.io/blog/2344-2/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_side_load_ccleaner_du.yml
author: X__Junior (Nextron Systems), Huntrule Team
date: 2023-07-13
tags:
  - attack.persistence
  - attack.privilege-escalation
  - attack.execution
  - attack.stealth
  - attack.t1574.001
logsource:
  category: image_load
  product: windows
detection:
  selection:
    ImageLoaded|endswith: \CCleanerDU.dll
  filter_main_path:
    Image|startswith:
      - C:\Program Files\CCleaner\
      - C:\Program Files (x86)\CCleaner\
    Image|endswith:
      - \CCleaner.exe
      - \CCleaner64.exe
  condition: selection and not 1 of filter_main_*
falsepositives:
  - False positives could occur from other custom installation paths. Apply additional filters accordingly.
level: medium
license: DRL-1.1
related:
  - id: 1fbc0671-5596-4e17-8682-f020a0b995dc
    type: derived

What it detects

This rule flags instances where Windows loads a DLL named "CCleanerDU.dll" when it is not associated with loading from the expected CCleaner installation executables. DLL sideloading is a common technique to execute attacker-controlled code by forcing a process to load a malicious or unintended DLL. The detection relies on image-load telemetry that records the loaded DLL path and the parent/executing image path (e.g., CCleaner.exe or CCleaner64.exe) to exclude likely legitimate loads.

Known false positives

False positives could occur from other custom installation paths. Apply additional filters accordingly.

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.