Windows process creation: WerFault.exe executed with -pr flag

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1036Masquerading
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags executions of WerFault.exe where the process creation command line includes the " -pr " argument. The behavior matters because this flag is used to run a file path stored in the ReflectDebugger registry location, which attackers may abuse to masquerade execution flow. Telemetry required is Windows process creation data containing the executable name and the full command line (including original filename metadata).

Reporting behind it

Related detections9 linkedT1036 — drag to rearrange

Suspicious Rclone Exfiltration Masquerading as wininit.exe

Suspicious Executable Running from Public Pictures Directory

Suspicious Python Execution via Renamed Synaptics Binary

Agent Tesla Persistence via Realtek Named Scheduled Task Batch

Suspicious Interlock Fake Updater Executable Execution

Malicious User Account Created by a Computer Account (via security)

Suspicious Execution of agent.exe From WinSyncDefender AppData Directory (via process_creation)

Malicious Scheduled Task Masquerading as Auto Update via schtasks (via process_creation)

Suspicious Novaservice Binary Executing From Public User Directory (via process_creation)

Windows process creation: WerFault.exe executed with -pr flag

Pivot detection · T1036 · 9 related

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

windows-process-creation-werfault-exe-executed-with-pr-flag-fabfb3a7

title: "Windows process creation: WerFault.exe executed with -pr flag"
id: f0825eba-bb67-470a-b1ee-a72462eb572d
related:
  - id: 0cf2e1c6-8d10-4273-8059-738778f981ad
    type: derived
  - id: fabfb3a7-3ce1-4445-9c7c-3c27f1051cdd
    type: derived
status: test
description: This rule flags executions of WerFault.exe where the process creation command line includes the " -pr " argument. The behavior matters because this flag is used to run a file path stored in the ReflectDebugger registry location, which attackers may abuse to masquerade execution flow. Telemetry required is Windows process creation data containing the executable name and the full command line (including original filename metadata).
references:
  - https://cocomelonc.github.io/malware/2022/11/02/malware-pers-18.html
  - https://www.hexacorn.com/blog/2018/08/31/beyond-good-ol-run-key-part-85/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_werfault_reflect_debugger_exec.yml
author: X__Junior (Nextron Systems), Huntrule Team
date: 2023-06-30
tags:
  - attack.execution
  - attack.stealth
  - attack.t1036
logsource:
  product: windows
  category: process_creation
detection:
  selection_img:
    - Image|endswith: \WerFault.exe
    - OriginalFileName: WerFault.exe
  selection_cli:
    CommandLine|contains: " -pr "
  condition: all of selection_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1

Convert

This rule as a query you can run. Uses no unlock credit.

SplunkSPL