Windows Devtunnels Image Loaded

SPLUNK detection rule by Raven Tait, Splunk · Apache-2.0

Detects image load events associated with Microsoft Devtunnels usage. Microsoft Devtunnels is a feature within Visual Studio that allows developers to expose their local development environment to the internet via secure, temporary tunnels, enabling external access for testing webhooks, APIs, and other services. While designed for legitimate development purposes, an attacker could exploit this feature to expose a compromised system or service to the internet, creating a covert communication channel that bypasses network security measures. By using Dev Tunnels, the attacker can establish a remote connection to the compromised environment, facilitate data exfiltration, or maintain command-and-control communications while avoiding detection by blending their activities with legitimate development traffic.

name: Windows Devtunnels Image Loaded
id: 15bb8eb7-8e68-490b-9032-18f7adce53c7
version: 2
creation_date: '2026-05-05'
modification_date: '2026-05-13'
author: Raven Tait, Splunk
status: production
type: Anomaly
description: |-
    Detects image load events associated with Microsoft Devtunnels usage.
    Microsoft Devtunnels is a feature within Visual Studio that allows developers to expose their local development environment to the internet via secure, temporary tunnels, enabling external access for testing webhooks, APIs, and other services.
    While designed for legitimate development purposes, an attacker could exploit this feature to expose a compromised system or service to the internet, creating a covert communication channel that bypasses network security measures.
    By using Dev Tunnels, the attacker can establish a remote connection to the compromised environment, facilitate data exfiltration, or maintain command-and-control communications while avoiding detection by blending their activities with legitimate development traffic.
data_source:
    - Sysmon EventID 7
search: |-
    `sysmon`
    EventID=7
    ImageLoaded="*\\AppData\\Local\\Temp\\.net\\devtunnel\\*"
    ImageLoaded="*devtunnel.dll"
    | fillnull
    | stats count min(_time) as firstTime
                  max(_time) as lastTime
      by Computer ImageLoaded EventID loaded_file loaded_file_path process_exec process_guid
         process_hash process_id process_name process_path service_dll_signature_exists
         service_dll_signature_verified signature_id user_id vendor_product

    | rename Computer as dest
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_devtunnels_image_loaded_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 the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. 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 `Processes` 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: Legitimate developers using Microsoft Devtunnels for testing and debugging may trigger this detection. Filter alerts for approved development environments and personnel.
references:
    - https://blueteamops.medium.com/detecting-dev-tunnels-16f0994dc3e2
drilldown_searches:
    - earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
      name: View the detection results for - "$user$" and "$dest$"
      search: '%original_detection_search% | search  user = "$user$" dest = "$dest$"'
    - name: View risk events for the last 7 days for - "$user$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | 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: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: Potential Devtunnels image load observed on $dest$ via $ImageLoaded$.
analytic_story:
    - Reverse Network Proxy
asset_type: Endpoint
mitre_attack_id:
    - T1090
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1090/snapattack/snapattack.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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