DLLHost with no Command Line Arguments with Network

SPLUNK detection rule by Steven Dick, Michael Haag, Splunk · Apache-2.0

The following analytic detects instances of DLLHost.exe running without command line arguments while establishing a network connection. This behavior is identified using Endpoint Detection and Response (EDR) telemetry, focusing on process execution and network activity data. It is significant because DLLHost.exe typically runs with specific arguments, and its absence can indicate malicious activity, such as Cobalt Strike usage. If confirmed malicious, this activity could allow attackers to execute code, move laterally, or exfiltrate data, posing a severe threat to the network's security.

name: DLLHost with no Command Line Arguments with Network
id: f1c07594-a141-11eb-8407-acde48001122
version: 17
creation_date: '2021-04-19'
modification_date: '2026-05-13'
author: Steven Dick, Michael Haag, Splunk
status: production
type: TTP
description: |
    The following analytic detects instances of DLLHost.exe running without
    command line arguments while establishing a network connection.
    This behavior is identified using Endpoint Detection and Response (EDR) telemetry,
    focusing on process execution and network activity data.
    It is significant because DLLHost.exe typically runs with specific arguments,
    and its absence can indicate malicious activity, such as Cobalt Strike usage.
    If confirmed malicious, this activity could allow attackers to execute code,
    move laterally, or exfiltrate data, posing a severe threat to the network's security.
data_source:
    - Sysmon EventID 1 AND Sysmon EventID 3
search: |
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
    as lastTime FROM datamodel=Endpoint.Processes where
    (
      Processes.process_name=dllhost.exe
      OR
      Processes.original_file_name=dllhost.exe
    )
    Processes.process IN (
      "*dllhost",
      "*dllhost.exe",
      "*dllhost.exe\""
    )
    by host _time span=1h
       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)`
    | rename dest as src
    | join host process_id
    [
      | tstats `security_content_summariesonly`
        count
        latest(All_Traffic.dest) as dest
        latest(All_Traffic.dest_ip) as dest_ip
        latest(All_Traffic.dest_port) as dest_port
        FROM datamodel=Network_Traffic.All_Traffic where
          All_Traffic.dest_port != 0
          by host All_Traffic.action All_Traffic.app All_Traffic.bytes All_Traffic.bytes_in
             All_Traffic.bytes_out All_Traffic.dest  All_Traffic.dest_ip All_Traffic.dest_port
             All_Traffic.dvc All_Traffic.protocol All_Traffic.protocol_version All_Traffic.src
             All_Traffic.src_ip All_Traffic.src_port All_Traffic.transport All_Traffic.user
             All_Traffic.vendor_product All_Traffic.direction All_Traffic.process_id
      | `drop_dm_object_name(All_Traffic)`
    ]
    | `dllhost_with_no_command_line_arguments_with_network_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: |
    Although unlikely, some legitimate third party applications
    may use a moved copy of dllhost, triggering a false positive.
references:
    - https://raw.githubusercontent.com/threatexpress/malleable-c2/c3385e481159a759f79b8acfe11acf240893b830/jquery-c2.4.2.profile
    - https://www.cobaltstrike.com/blog/learn-pipe-fitting-for-all-of-your-offense-projects/
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: The process $process_name$ was spawned by $parent_process_name$ without any command-line arguments on $src$ by $user$.
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: The process $process_name$ was spawned by $parent_process_name$ without any command-line arguments on $src$ by $user$.
threat_objects:
    - field: parent_process_name
      type: process
    - field: process_name
      type: process_name
analytic_story:
    - BlackByte Ransomware
    - Cobalt Strike
    - Graceful Wipe Out Attack
    - Cactus Ransomware
    - Storm-2460 CLFS Zero Day Exploitation
    - Earth Alux
asset_type: Endpoint
mitre_attack_id:
    - T1055
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/cobalt_strike/windows-sysmon_dllhost.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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