Windows Process Execution with User Name "ANONYMOUS" from System32 or AppData
Alerts on Windows process executions where the user is marked "ANONYMOUS" and the parent path is in System32 or AppData.
FreeReviewedSigma · High · v5
- Product
- windows
- Category
- process_creation
- Author
- Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2023-04-30
- Updated
- 2026-07-31
What it detects
This rule flags Windows process creation events where the process runs under a user value containing "ANONYMOUS" and the parent image path contains either "\Windows\System32\" or "\AppData\". Attackers may use an anonymous or placeholder user context to obscure execution provenance and evade straightforward user-based monitoring. Detection relies on process creation telemetry that includes the parent image path and the user field associated with the created process.
Reporting behind it
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No 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-process-creation-by-anonymous-user-with-system32-appdata-parent-image-e01b6eb5
title: Windows Process Execution with User Name "ANONYMOUS" from System32 or AppData
id: 89449b58-b4d7-4a1a-aed7-e910cd08a833
status: test
description: This rule flags Windows process creation events where the process runs under a user value containing "ANONYMOUS" and the parent image path contains either "\Windows\System32\" or "\AppData\". Attackers may use an anonymous or placeholder user context to obscure execution provenance and evade straightforward user-based monitoring. Detection relies on process creation telemetry that includes the parent image path and the user field associated with the created process.
references:
- https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/cold-steel/NCSC-MAR-Cold-Steel.pdf
- https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2023/Malware/COLDSTEEL/proc_creation_win_malware_coldsteel_anonymous_process.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-04-30
tags:
- attack.persistence
- detection.emerging-threats
- attack.stealth
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage|contains:
- \Windows\System32\
- \AppData\
User|contains: ANONYMOUS
condition: selection
falsepositives:
- Unknown
level: high
license: DRL-1.1
related:
- id: e01b6eb5-1eb4-4465-a165-85d40d874add
type: derived