Shai-Hulud Workflow File Creation or Modification

name: Shai-Hulud Workflow File Creation or Modification
id: 6b4a0a7f-10d1-4d72-9c4c-5c6a3d9f9d6a
version: 2
date: '2026-03-10'
author: Michael Haag, Splunk
status: production
type: TTP
description: |
    Detects creation or deletion of malicious GitHub Actions workflow files associated with
    Shai-Hulud worm variants on Linux or Windows endpoints. This includes the original shai-hulud-workflow.yml,
    the 2.0 backdoor discussion.yaml (enables command injection via GitHub Discussions on self-hosted
    runners named SHA1HULUD), and the secrets exfiltration workflow formatter_*.yml pattern. These
    files are used to exfiltrate credentials and propagate across repositories.
data_source:
    - Sysmon for Linux EventID 11
    - Sysmon EventID 11
search: |
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime

    from datamodel=Endpoint.Filesystem where

    Filesystem.file_path IN (
      "*/.github/workflows/discussion.yaml",
      "*/.github/workflows/discussion.yml",
      "*/.github/workflows/formatter_*.yaml",
      "*/.github/workflows/formatter_*.yml",
      "*/.github/workflows/shai-hulud-workflow.yaml",
      "*/.github/workflows/shai-hulud-workflow.yml",
      "*/.github/workflows/shai-hulud.yaml",
      "*/.github/workflows/shai-hulud.yml",
      "*\\.github\\workflows\\discussion.yaml",
      "*\\.github\\workflows\\discussion.yml",
      "*\\.github\\workflows\\formatter_*.yaml",
      "*\\.github\\workflows\\formatter_*.yml",
      "*\\.github\\workflows\\shai-hulud-workflow.yaml",
      "*\\.github\\workflows\\shai-hulud-workflow.yml",
      "*\\.github\\workflows\\shai-hulud.yaml",
      "*\\.github\\workflows\\shai-hulud.yml"
    )

    by Filesystem.action Filesystem.dest Filesystem.file_access_time Filesystem.file_create_time
       Filesystem.file_hash Filesystem.file_modify_time Filesystem.file_name Filesystem.file_path Filesystem.file_acl Filesystem.file_size Filesystem.process_guid Filesystem.process_id Filesystem.user
       Filesystem.vendor_product

    | `drop_dm_object_name(Filesystem)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `shai_hulud_workflow_file_creation_or_modification_filter`
how_to_implement: |
    The detection is based on data that originates from Endpoint Detection
    and Response (EDR) agents. These agents are designed to provide security-related
    telemetry from the endpoints where the agent is installed. To implement this search,
    you must ingest logs that contain filesystem events, specifically file creation
    and deletion events. These logs must be processed using the appropriate Splunk
    Technology Add-ons that are specific to the EDR product. The logs must also be
    mapped to the `Filesystem` node of the `Endpoint` data model. Use the Splunk Common
    Information Model (CIM) to normalize the field names and speed up the data modeling
    process.
known_false_positives: |
    Very low. Legitimate usage of a file with this exact name is unlikely; validate with repository owners.
references:
    - https://www.wiz.io/blog/shai-hulud-2-0-ongoing-supply-chain-attack
    - https://securelist.com/shai-hulud-worm-infects-500-npm-packages-in-a-supply-chain-attack/117547/
    - https://github.com/SigmaHQ/sigma/pull/5658/files
    - https://www.cisa.gov/news-events/alerts/2025/09/23/widespread-supply-chain-compromise-impacting-npm-ecosystem
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: Shai-Hulud malicious workflow file detected on endpoint $dest$ at $file_path$. Immediate investigation required.
    risk_objects:
        - field: dest
          type: system
          score: 50
    threat_objects:
        - field: file_path
          type: file_path
tags:
    analytic_story:
        - NPM Supply Chain Compromise
    asset_type: Endpoint
    mitre_attack_id:
        - T1574.006
        - T1554
        - T1195
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test - Linux
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1195.001/npm/shai_hulud_workflow_sysmon.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux
    - name: True Positive Test - Windows
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1195.001/npm/windows_workflow_sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog