Windows Universal Data Link File Creation

name: Windows Universal Data Link File Creation
id: aac9ade1-dc8b-4f15-9586-4665d01b8645
version: 2
creation_date: '2021-09-02'
modification_date: '2026-05-13'
author: Raven Tait, Splunk
status: production
type: Anomaly
description: |-
    Detects the creation of Universal Data Link (UDL) files.
    This could indicate a phishing technique that exploits UDL files, which are typically used in Windows for database connections.
    Attackers might leverage UDL files to bypass email filters and capture user credentials by tricking victims into testing a connection to a malicious server.
data_source:
    - Sysmon EventID 11
search: |-
    | tstats `security_content_summariesonly`
      count min(_time) as firstTime
            max(_time) as lastTime
    
    from datamodel=Endpoint.Filesystem where
    
    Filesystem.file_name="*.udl"
    Filesystem.action="created"
    
    by Filesystem.dest Filesystem.file_create_time Filesystem.process_path
       Filesystem.process_guid Filesystem.process_id Filesystem.file_path
       Filesystem.action Filesystem.file_name Filesystem.user
       Filesystem.vendor_product
    
    | `drop_dm_object_name(Filesystem)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_universal_data_link_file_creation_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 database administrators or developers may create UDL files for routine connection testing. Filter alerts based on trusted user activity to reduce false positives.
references:
    - https://trustedsec.com/blog/oops-i-udld-it-again
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: UDL file created at $file_path$ on $dest$.
threat_objects:
    - field: file_path
      type: file_path
analytic_story:
    - Spearphishing Attachments
asset_type: Endpoint
mitre_attack_id:
    - T1204.002
    - T1566.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint