huntrule

Windows PFX File Creation From File Events

Flags Windows file events where a .pfx (certificate + private key) is created, excluding a few common benign locations.

FreeReviewedSigma · Low · v5
Product
windows
Category
file_event
Author
Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research) (SigmaHQ), DRL 1.1
Published
2020-05-02
Updated
2026-07-31
AnalysisDetection
title: Windows PFX File Creation From File Events
id: 243aff18-74ca-4c33-a615-ee5fe46fc43b
status: test
description: This rule identifies creation of Personal Information Exchange (PFX) files by matching file events where the target filename ends with .pfx. Because PFX files bundle private keys and certificates, their creation can indicate attempts to collect credentials for impersonation or signing, or to stage certificate-based access. The detection relies on Windows file event telemetry and uses exclusion filters for common benign locations and tooling-related PFX generation (such as OneDrive CodeSigning.pfx, Visual Studio, and CMake paths).
references:
  - https://github.com/OTRF/detection-hackathon-apt29/issues/14
  - https://github.com/OTRF/ThreatHunter-Playbook/blob/2d4257f630f4c9770f78d0c1df059f891ffc3fec/docs/evals/apt29/detections/6.B.1_6392C9F1-D975-4F75-8A70-433DEDD7F622.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/file/file_event/file_event_win_pfx_file_creation.yml
author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research), Huntrule Team
date: 2020-05-02
modified: 2025-10-19
tags:
  - attack.credential-access
  - attack.t1552.004
  - detection.threat-hunting
logsource:
  product: windows
  category: file_event
detection:
  selection:
    TargetFilename|endswith: .pfx
  filter_optional_onedrive:
    Image:
      - C:\Program Files\Microsoft OneDrive\OneDrive.exe
      - C:\Program Files (x86)\Microsoft OneDrive\OneDrive.exe
    TargetFilename|endswith: \OneDrive\CodeSigning.pfx
  filter_optional_visual_studio:
    TargetFilename|startswith:
      - C:\Program Files (x86)\Microsoft Visual Studio\
      - C:\Program Files\Microsoft Visual Studio\
  filter_optional_cmake:
    TargetFilename|startswith: C:\Program Files\CMake\
  condition: selection and not 1 of filter_optional_*
falsepositives:
  - System administrators legitimately managing certificates and PKI infrastructure
  - Development environments where developers create test certificates for application signing
  - Automated certificate deployment tools and scripts used in enterprise environments
  - Software installation processes that include certificate provisioning (e.g., web servers, VPN clients)
  - Certificate backup and recovery operations performed by IT staff
  - Build systems and CI/CD pipelines that generate code signing certificates
  - Third-party applications that create temporary certificates for secure communications
level: low
license: DRL-1.1
related:
  - id: dca1b3e8-e043-4ec8-85d7-867f334b5724
    type: derived