Rundll32 Control RunDLL World Writable Directory

name: Rundll32 Control RunDLL World Writable Directory
id: 1adffe86-10c3-11ec-8ce6-acde48001122
version: 13
creation_date: '2021-09-08'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic detects the execution of rundll32.exe with the `Control_RunDLL` command, loading files from world-writable directories such as windows\temp, programdata, or appdata. This detection leverages Endpoint Detection and Response (EDR) telemetry, focusing on process command-line data and specific directory paths. This activity is significant as it may indicate an attempt to exploit CVE-2021-40444 or similar vulnerabilities, allowing attackers to execute arbitrary code. If confirmed malicious, this could lead to unauthorized code execution, privilege escalation, or persistent access within the environment.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_rundll32` Processes.process=*Control_RunDLL* AND Processes.process IN ("*\\appdata\\*", "*\\windows\\temp\\*", "*\\programdata\\*") by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `rundll32_control_rundll_world_writable_directory_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: This may be tuned, or a new one related, by adding .cpl to command-line. However, it's important to look for both. Tune/filter as needed.
references:
    - https://strontic.github.io/xcyclopedia/library/rundll32.exe-111474C61232202B5B588D2B512CBB25.html
    - https://app.any.run/tasks/36c14029-9df8-439c-bba0-45f2643b0c70/
    - https://attack.mitre.org/techniques/T1218/011/
    - https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444
    - https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.002/T1218.002.yaml
    - https://redcanary.com/blog/intelligence-insights-december-2021/
finding:
    title: An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to load a suspicious file from disk.
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to load a suspicious file from disk.
threat_objects:
    - field: parent_process_name
      type: parent_process_name
    - field: process_name
      type: process_name
analytic_story:
    - Microsoft MSHTML Remote Code Execution CVE-2021-40444
    - Suspicious Rundll32 Activity
    - Living Off The Land
    - Compromised Windows Host
asset_type: Endpoint
cve:
    - CVE-2021-40444
mitre_attack_id:
    - T1218.011
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint