Potentially Suspicious Rundll32.EXE Execution of UDL File (via process_creation)

title: Potentially Suspicious Rundll32.EXE Execution of UDL File (via process_creation)
id: 5051e1c7-4b8c-5b68-a0d5-e5a4db62c5a1
status: stable
description: This rule detects the execution of rundll32.exe with the oledb32.dll library to open a UDL file. Threat actors can misuse this method as a phishing vector to capture authentication credentials or other sensitive data.
references:
    - https://attack.mitre.org/techniques/T1071/
    - https://attack.mitre.org/techniques/T1218/011/
    - https://trustedsec.com/blog/oops-i-udld-it-again
author: 'Huntrule Team'
date: 2026-04-12
tags:
    - attack.execution
    - attack.command-and-control
    - attack.stealth
    - attack.t1218.011
    - attack.t1071
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\explorer.exe'
    selection_img:
        - Image|endswith: '\rundll32.exe'
        - OriginalFileName: 'RUNDLL32.EXE'
    selection_cli:
        CommandLine|contains|all:
            - 'oledb32.dll'
            - ',OpenDSLFile '
            - '\\Users\\*\\Downloads\\'
        CommandLine|endswith: '.udl'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium