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Detection rules › Splunk

Windows Executable in Loaded Modules

Status
production
Severity
medium
Group by
Signed, dest, image_loaded, process_guid, process_hash, process_id, process_name, service_dll_signature_exists, service_dll_signature_verified, signature, signature_id, user_id, vendor_product
Author
Teoderick Contreras, Splunk
Source
github.com/splunk/security_content

The following analytic identifies instances where executable files (.exe) are loaded as modules, detected through 'ImageLoaded' events in Sysmon logs. This method leverages Sysmon EventCode 7 to track unusual module loading behavior, which is significant as it deviates from the norm of loading .dll files. This activity is crucial for SOC monitoring because it can indicate the presence of malware like NjRAT, which uses this technique to load malicious modules. If confirmed malicious, this behavior could allow attackers to execute arbitrary code, maintain persistence, and further compromise the host system.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1129 Shared Modules

Event coverage

ProviderEventTitle
SysmonEvent ID 7Image loaded

Rule body splunk

name: Windows Executable in Loaded Modules
id: 3e27af56-fcf0-4113-988d-24969b062be7
version: 12
creation_date: '2023-09-19'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic identifies instances where executable files (.exe) are loaded as modules, detected through 'ImageLoaded' events in Sysmon logs. This method leverages Sysmon EventCode 7 to track unusual module loading behavior, which is significant as it deviates from the norm of loading .dll files. This activity is crucial for SOC monitoring because it can indicate the presence of malware like NjRAT, which uses this technique to load malicious modules. If confirmed malicious, this behavior could allow attackers to execute arbitrary code, maintain persistence, and further compromise the host system.
data_source:
    - Sysmon EventID 7
search: |-
    `sysmon` EventCode=7 ImageLoaded != *.dll AND Signed != true
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY Image ImageLoaded dest
           loaded_file loaded_file_path original_file_name
           process_exec process_guid process_hash
           process_id process_name process_path
           service_dll_signature_exists service_dll_signature_verified signature
           Signed signature_id user_id
           vendor_product
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `windows_executable_in_loaded_modules_filter`
how_to_implement: To successfully implement this search, you need to be ingesting logs with the process name and imageloaded executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.
known_false_positives: No false positives have been identified at this time.
references:
    - https://malpedia.caad.fkie.fraunhofer.de/details/win.njrat
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 executable $ImageLoaded$ loaded by $Image$ on $dest$
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - NjRAT
    - Lokibot
asset_type: Endpoint
mitre_attack_id:
    - T1129
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/T1129/executable_shared_modules/image_loaded_exe.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

Stages and Predicates

Stage 1: search

`sysmon` EventCode=7 ImageLoaded != *.dll AND Signed != true

Stage 2: fillnull

| fillnull

Stage 3: stats

| stats count min(_time) as firstTime max(_time) as lastTime
    BY Image ImageLoaded dest
       loaded_file loaded_file_path original_file_name
       process_exec process_guid process_hash
       process_id process_name process_path
       service_dll_signature_exists service_dll_signature_verified signature
       Signed signature_id user_id
       vendor_product

Stage 4: search

| `security_content_ctime(firstTime)`

Stage 5: search

| `security_content_ctime(lastTime)`

Stage 6: search

| `windows_executable_in_loaded_modules_filter`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
EventCodeeq
  • 7 corpus 39 (splunk 38, kusto 1)
ImageLoadedne
  • *.dll
Signedne
  • true