GitHub Repo

Detection: Windows Theme File Creation in Unusual Location

Updated Date: 2026-04-13 ID: a11f5f36-2c32-4323-8cb0-0fec84b3188d Author: Raven Tait, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

Detects theme files being created in unusual locations. These files, used to customize desktop appearances, have been used for remote code execution and NTLM coercion attacks.

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Endpoint.Filesystem where
 7
 8Filesystem.file_path IN (
 9    "*\\Desktop\\*",
10    "*\\Documents\\*",
11    "*\\Downloads\\*",
12    "*\\Temp\\*"
13)
14Filesystem.file_name="*.theme"
15Filesystem.action="created"
16
17by Filesystem.dest Filesystem.file_create_time Filesystem.process_path
18   Filesystem.process_guid Filesystem.process_id Filesystem.file_path
19   Filesystem.action Filesystem.file_name
20   Filesystem.user Filesystem.vendor_product
21
22
23| `drop_dm_object_name(Filesystem)`
24
25| `security_content_ctime(firstTime)`
26
27| `security_content_ctime(lastTime)`
28
29| `windows_theme_file_creation_in_unusual_location_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 11 Windows icon Windows 'XmlWinEventLog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_theme_file_creation_in_unusual_location_filter search *
windows_theme_file_creation_in_unusual_location_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1187 Forced Authentication Credential Access
T1557.001 Name Resolution Poisoning and SMB Relay Collection
T1021.002 SMB/Windows Admin Shares Credential Access
Exploitation
DE.AE
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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

Legitimate customization or IT management may use theme files that trigger this detection. Review and allow trusted themes from authorized sources.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Windows theme file created in unusual location at $file_path$ on $dest$.

Risk Object Risk Object Type Risk Score Threat Objects
dest system 20 file_path

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1