Access To Windows DPAPI Master Keys By Uncommon Applications — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-10-17 / 2024-07-29.

{
  "category": "file_access",
  "product": "windows",
  "definition": "Requirements: Microsoft-Windows-Kernel-File ETW provider"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 231e075f9e7932bd4127e0c17996434a2f442f4a2e240933d5f9d3c15e890d81

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Access To Windows DPAPI Master Keys By Uncommon Applications
id: 46612ae6-86be-4802-bc07-39b59feb1309
status: test
description: |
    Detects file access requests to the the Windows Data Protection API Master keys by an uncommon application.
    This can be a sign of credential stealing. Example case would be usage of mimikatz "dpapi::masterkey" function
references:
    - http://blog.harmj0y.net/redteaming/operational-guidance-for-offensive-user-dpapi-abuse/
    - https://book.hacktricks.xyz/windows-hardening/windows-local-privilege-escalation/dpapi-extracting-passwords
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-10-17
modified: 2024-07-29
tags:
    - attack.credential-access
    - attack.t1555.004
logsource:
    category: file_access
    product: windows
    definition: 'Requirements: Microsoft-Windows-Kernel-File ETW provider'
detection:
    selection:
        FileName|contains:
            - '\Microsoft\Protect\S-1-5-18\' # For System32
            - '\Microsoft\Protect\S-1-5-21-' # For Users
    filter_system_folders:
        Image|startswith:
            - 'C:\Program Files\'
            - 'C:\Program Files (x86)\'
            - 'C:\Windows\system32\'
            - 'C:\Windows\SysWOW64\'
    condition: selection and not 1 of filter_*
falsepositives:
    - Unknown
# Increase level after false positives filters are good enough
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• http://blog.harmj0y.net/redteaming/operational-guidance-for-offensive-user-dpapi-abuse/
• https://book.hacktricks.xyz/windows-hardening/windows-local-privilege-escalation/dpapi-extracting-passwords