splunk_escuAnomaly

Windows Executable Masquerading as Benign File Types

The following analytic detects the presence of executable files masquerading as benign file types on Windows systems. Adversaries employ this technique to evade defenses and trick users into executing malicious code by renaming executables with extensions commonly associated with documents, images, or other non-executable formats (e.g., .pdf, .jpg, .doc, .png).

MITRE ATT&CK

T1036.008

defense-evasion

Detection Query

`sysmon`
EventCode=29
NOT `executable_extensions`
| stats count min(_time) as firstTime max(_time) as lastTime
  by Image file_name file_path process_guid file_hash process_id dest user EventCode
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `windows_executable_masquerading_as_benign_file_types_filter`

Author

Teoderick Contreras, Splunk

Created

2026-03-10

Data Sources

Sysmon EventID 29

References

Tags

NetSupport RMM Tool Abuse

Raw Content

name: Windows Executable Masquerading as Benign File Types
id: 0470c8e7-dd8d-420f-8302-073e8a2b66f0
version: 3
date: '2026-03-10'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: |
    The following analytic detects the presence of executable files masquerading as benign file types on Windows systems. Adversaries employ this technique to evade defenses and trick users into executing malicious code by renaming executables with extensions commonly associated with documents, images, or other non-executable formats (e.g., .pdf, .jpg, .doc, .png).
data_source:
    - Sysmon EventID 29
search: |
    `sysmon`
    EventCode=29
    NOT `executable_extensions`
    | stats count min(_time) as firstTime max(_time) as lastTime
      by Image file_name file_path process_guid file_hash process_id dest user EventCode
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_executable_masquerading_as_benign_file_types_filter`
how_to_implement: |
    To implement Sysmon EventCode 29 (File Block Executable), you must ensure that your Sysmon deployment is configured to log instances where executable file creation is blocked based on your organization's FileBlockExecutable rules. Once enabled, the corresponding Splunk search requires Sysmon operational logs and an input macro named sysmon, which should be customized to match your environment-specific index, source, and sourcetype settings for Windows Sysmon data. We strongly recommend replacing this macro with values appropriate to your Splunk environment so the search scopes correctly. The search also uses a post-filter macro designed to filter out known false positives.
known_false_positives: |
    File types that are not included in the filter for this detection may generate false positives, so proper filtering is required.
references:
    - https://www.linkedin.com/posts/mauricefielenbach_cybersecurity-incidentresponse-dfir-activity-7394805779448418304-g0gZ?utm_source=share&utm_medium=member_desktop&rcm=ACoAAAuFTjIB5weY_kcyu4qp3kHbI4v49tO0zEk
    - https://www.blackhillsinfosec.com/a-sysmon-event-id-breakdown/
    - https://thedfirreport.com/2023/10/30/netsupport-intrusion-results-in-domain-compromise/
    - https://www.esentire.com/blog/evalusion-campaign-delivers-amatera-stealer-and-netsupport-rat
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 ("$dest$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: A valid Windows PE executable $file_name$ located in $file_path$ was dropped on $dest$, disguised as a non-executable file type.
    risk_objects:
        - field: dest
          type: system
          score: 20
    threat_objects:
        - field: Image
          type: process
        - field: file_name
          type: file_name
        - field: file_path
          type: file_path
tags:
    analytic_story:
        - NetSupport RMM Tool Abuse
    asset_type: Endpoint
    mitre_attack_id:
        - T1036.008
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1036.008/masquerading_executable_as_non_exec_file_type/non_exec_ext_but_exec_detected.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog