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Detection rules › Splunk

Windows Admin Permission Discovery

Status
production
Severity
low
Group by
CreationUtcTime, computer_name, event_action, file_access_time, file_acl, file_hash, file_modify_time, file_name, file_size, process_guid, process_id, target_filename, user, vendor_product
Author
Teoderick Contreras, Splunk
Source
github.com/splunk/security_content

The following analytic identifies the creation of a suspicious file named 'win.dat' in the root directory (C:). It leverages data from the Endpoint.Filesystem datamodel to detect this activity. This behavior is significant as it is commonly used by malware like NjRAT to check for administrative privileges on a compromised host. If confirmed malicious, this activity could indicate that the malware has administrative access, allowing it to perform high-privilege actions, potentially leading to further system compromise and persistence.

Known false positives

  • False positives may occur if there are legitimate accounts with the privilege to drop files in the root of the C drive. It's recommended to verify the legitimacy of such actions and the accounts involved.

MITRE ATT&CK coverage

TacticTechniques
Discovery

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 11: FileCreate

Rule body

name: Windows Admin Permission Discovery
id: e08620cb-9488-4052-832d-97bcc0afd414
version: 9
creation_date: '2023-09-21'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: The following analytic identifies the creation of a suspicious file named 'win.dat' in the root directory (C:\). It leverages data from the Endpoint.Filesystem datamodel to detect this activity. This behavior is significant as it is commonly used by malware like NjRAT to check for administrative privileges on a compromised host. If confirmed malicious, this activity could indicate that the malware has administrative access, allowing it to perform high-privilege actions, potentially leading to further system compromise and persistence.
data_source:
    - Sysmon EventID 11
search: '|tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.exe", "*.dll", "*.sys", "*.com", "*.vbs", "*.vbe", "*.js", "*.bat", "*.cmd", "*.pif", "*.lnk", "*.dat") by Filesystem.action Filesystem.dest Filesystem.file_access_time Filesystem.file_create_time Filesystem.file_hash Filesystem.file_modify_time Filesystem.file_name Filesystem.file_path Filesystem.file_acl Filesystem.file_size Filesystem.process_guid Filesystem.process_id Filesystem.user Filesystem.vendor_product | `drop_dm_object_name(Filesystem)` | eval dropped_file_path = split(file_path, "\\") | eval dropped_file_path_split_count = mvcount(dropped_file_path) | eval root_drive = mvindex(dropped_file_path,0) | where LIKE(root_drive, "C:") AND dropped_file_path_split_count = 2 | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_admin_permission_discovery_filter`'
how_to_implement: To successfully implement this search you need to be ingesting information on process that include the name of the Filesystem responsible for the changes from your endpoints into the `Endpoint` datamodel in the `Filesystem` node.
known_false_positives: False positives may occur if there are legitimate accounts with the privilege to drop files in the root of the C drive. It's recommended to verify the legitimacy of such actions and the accounts involved.
references:
    - https://malpedia.caad.fkie.fraunhofer.de/details/win.njrat
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: A file was created in root drive C:/ on host - $dest$
threat_objects:
    - field: file_name
      type: file_name
analytic_story:
    - NjRAT
asset_type: Endpoint
mitre_attack_id:
    - T1069.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint

Stages and Predicates

Stage 1: tstats

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.exe", "*.dll", "*.sys", "*.com", "*.vbs", "*.vbe", "*.js", "*.bat", "*.cmd", "*.pif", "*.lnk", "*.dat") by Filesystem.action Filesystem.dest Filesystem.file_access_time Filesystem.file_create_time Filesystem.file_hash Filesystem.file_modify_time Filesystem.file_name Filesystem.file_path Filesystem.file_acl Filesystem.file_size Filesystem.process_guid Filesystem.process_id Filesystem.user Filesystem.vendor_product

Stage 2: search

| `drop_dm_object_name(Filesystem)`

Stage 3: eval

| eval dropped_file_path = split(file_path, "\\")

Stage 4: eval

| eval dropped_file_path_split_count = mvcount(dropped_file_path)

Stage 5: eval

| eval root_drive = mvindex(dropped_file_path,0)

Stage 6: where

| where LIKE(root_drive, "C:") AND dropped_file_path_split_count = 2

Stage 7: search

| `security_content_ctime(firstTime)`

Stage 8: search

| `security_content_ctime(lastTime)`

Stage 9: search

| `windows_admin_permission_discovery_filter`

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Filesystem.file_namein
  • "*.bat"
  • "*.cmd"
  • "*.com"
  • "*.dat"
  • "*.dll" corpus 7 (splunk 6, kusto 1)
  • "*.exe" corpus 2 (kusto 2)
  • "*.js"
  • "*.lnk"
  • "*.pif"
  • "*.sys"
  • "*.vbe"
  • "*.vbs"
field:"file_name" kind:in
dropped_file_path_split_counteq
  • 2 corpus 2 (splunk 2)
field:"dropped_file_path_split_count" kind:eq value:"2"
root_drivelike
  • "C:"
field:"root_drive" kind:like