Windows Rasautou DLL Execution

name: Windows Rasautou DLL Execution
id: 6f42b8be-8e96-11ec-ad5a-acde48001122
version: 15
creation_date: '2022-02-09'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic detects the execution of an arbitrary DLL by the Windows Remote Auto Dialer (rasautou.exe). This behavior is identified by analyzing process creation events where rasautou.exe is executed with specific command-line arguments. This activity is significant because it leverages a Living Off The Land Binary (LOLBin) to execute potentially malicious code, bypassing traditional security controls. If confirmed malicious, this technique could allow an attacker to execute arbitrary code, potentially leading to system compromise, 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 Processes.process_name=rasautou.exe Processes.process="* -d *"AND Processes.process="* -p *"
      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)`
    | `windows_rasautou_dll_execution_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: False positives will be limited to applications that require Rasautou.exe to load a DLL from disk. Filter as needed.
references:
    - https://github.com/mandiant/DueDLLigence
    - https://github.com/MHaggis/notes/blob/master/utilities/Invoke-SPLDLLigence.ps1
    - https://gist.github.com/NickTyrer/c6043e4b302d5424f701f15baf136513
    - https://www.mandiant.com/resources/staying-hidden-on-the-endpoint-evading-detection-with-shellcode
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 ("$dest$") | 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"
finding:
    title: An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ attempting to load a DLL in a suspicious manner.
    entity:
        field: dest
        type: system
        score: 50
threat_objects:
    - field: parent_process_name
      type: parent_process_name
    - field: process_name
      type: process_name
analytic_story:
    - Compromised Windows Host
    - Windows Defense Evasion Tactics
    - Hellcat Ransomware
asset_type: Endpoint
mitre_attack_id:
    - T1055.001
    - T1218
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/T1055.001/rasautou/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit