Windows File Writes Matching DPAPI Backup Key and Certificate Export Filenames

Alerts on Windows file events for DPAPI backup key/certificate filenames ending in .cer/.key/.pfx/.pvk.

FreeReviewedSigma · High · v2

Product: windows
Category: file_event
Author: Nounou Mbeiri, Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2024-06-26
Updated: 2026-07-31

ATT&CK techniques

Cred Access

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
- T1552.004Private Keys
- T1555Credentials from Password Stores
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

Identifies Windows file events where the target filename contains DPAPI-related backup key prefixes (ntds_capi_, ntds_legacy_, ntds_unknown_) and ends with certificate/key extensions (.cer, .key, .pfx, .pvk). This pattern is commonly associated with tools that export or steal DPAPI backup keys and certificates, which attackers can use to decrypt protected credentials. Detection relies on file event telemetry that includes the target filename.

Reporting behind it

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Possible SCOM RunAs Credential Theft via Access to Common MOMBins Encryption Key

Suspicious AMOS Stealer Fake Password Prompt via osascript (via process_creation)

Suspicious macOS Credential Validation via dscl authonly

Malicious Browser Credential Theft via rundll32 Loading move.dll (via process_creation)

Suspicious Data Exfiltration via curl Multipart Upload to Gate Endpoint

Suspicious ALPHA SPIDER Veeam Backup Credential Extraction (via process_creation)

Windows File Writes Matching DPAPI Backup Key and Certificate Export Filenames

Pivot detection · T1555 · 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-file-creation-of-dpapi-backup-key-and-certificate-export-files-7892ec59

title: Windows File Writes Matching DPAPI Backup Key and Certificate Export Filenames
id: e3a028db-f1b2-4609-825b-507d2ea26e5f
status: test
description: Identifies Windows file events where the target filename contains DPAPI-related backup key prefixes (ntds_capi_, ntds_legacy_, ntds_unknown_) and ends with certificate/key extensions (.cer, .key, .pfx, .pvk). This pattern is commonly associated with tools that export or steal DPAPI backup keys and certificates, which attackers can use to decrypt protected credentials. Detection relies on file event telemetry that includes the target filename.
references:
  - https://www.dsinternals.com/en/dpapi-backup-key-theft-auditing/
  - https://github.com/MichaelGrafnetter/DSInternals/blob/39ee8a69bbdc1cfd12c9afdd7513b4788c4895d4/Src/DSInternals.Common/Data/DPAPI/DPAPIBackupKey.cs#L28-L32
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_susp_dpapi_backup_and_cert_export_ioc.yml
author: Nounou Mbeiri, Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2024-06-26
tags:
  - attack.credential-access
  - attack.t1555
  - attack.t1552.004
logsource:
  product: windows
  category: file_event
detection:
  selection:
    TargetFilename|contains:
      - ntds_capi_
      - ntds_legacy_
      - ntds_unknown_
    TargetFilename|endswith:
      - .cer
      - .key
      - .pfx
      - .pvk
  condition: selection
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: 7892ec59-c5bb-496d-8968-e5d210ca3ac4
    type: derived

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