Windows DLL Sideloading: CCleanerReactivator.dll Loaded from CCleaner Directories

Identifies potential CCleanerReactivator.dll DLL sideloading when loaded by CCleanerReactivator.exe outside expected CCleaner paths.

FreeReviewedSigma · Medium · v2

Product: windows
Category: image_load
Author: X__Junior (SigmaHQ), DRL 1.1
Published: 2023-07-13
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1574.001DLL
Persistence
- T1574.001DLL
Priv Esc
- T1574.001DLL
Defense Evasion
- T1574.001DLL
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

Flags Windows processes that load CCleanerReactivator.dll from an image path ending with \\CCleanerReactivator.dll while the loader executable matches CCleanerReactivator.exe in common CCleaner install locations. DLL sideloading is a stealthy way for an attacker to run malicious code by planting or swapping a DLL that a legitimate executable expects. The rule relies on image load telemetry, matching the loaded DLL name and the loading process path under Program Files locations.

Reporting behind it

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Windows DLL Sideloading: CCleanerReactivator.dll Loaded from CCleaner Directories

Pivot detection · T1574.001 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

windows-dll-sideloading-attempts-ccleanerreactivator-dll-loaded-by-ccleanerreact-3735d5ac

title: "Windows DLL Sideloading: CCleanerReactivator.dll Loaded from CCleaner Directories"
id: 269c3465-100b-43a9-8a91-06d101e1e1fe
status: test
description: Flags Windows processes that load CCleanerReactivator.dll from an image path ending with \\CCleanerReactivator.dll while the loader executable matches CCleanerReactivator.exe in common CCleaner install locations. DLL sideloading is a stealthy way for an attacker to run malicious code by planting or swapping a DLL that a legitimate executable expects. The rule relies on image load telemetry, matching the loaded DLL name and the loading process path under Program Files locations.
references:
  - https://lab52.io/blog/2344-2/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_side_load_ccleaner_reactivator.yml
author: X__Junior, 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: \CCleanerReactivator.dll
  filter_main_path:
    Image|startswith:
      - C:\Program Files\CCleaner\
      - C:\Program Files (x86)\CCleaner\
    Image|endswith: \CCleanerReactivator.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: 3735d5ac-d770-4da0-99ff-156b180bc600
    type: derived

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