Detection: Windows Alternate DataStream - Executable Content

Updated Date: 2026-05-13 ID: a258bf2a-34fd-4986-8086-78f506e00206 Author: Steven Dick, Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the writing of data with an IMPHASH value to an Alternate Data Stream (ADS) in the NTFS file system. It leverages Sysmon Event ID 15 and regex to identify files with a Portable Executable (PE) structure. This activity is significant as it may indicate a threat actor staging malicious code in hidden areas for persistence or future execution. If confirmed malicious, this could allow attackers to execute hidden code, maintain persistence, or escalate privileges within the environment.

Search

1`sysmon` EventCode=15 IMPHASH!=00000000000000000000000000000000 
2| regex TargetFilename="(?<!\/)\b\w+(\.\w+)?:\w+(\.\w+)?$" 
3| eval file_name = replace(TargetFilename,"(.*\\\)",""), process = Image , file_path = TargetFilename, file_hash = coalesce(SHA256,SHA1,MD5,Hash) 
4| stats count min(_time) as firstTime max(_time) as lastTime by dest dvc file_hash file_name file_path process_exec process_guid process_id process_name process_path signature signature_id user_id vendor_product Contents Image 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `windows_alternate_datastream___executable_content_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 15	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
sysmon	`(source=WinEventLog:Microsoft-Windows-Sysmon/Operational OR source=XmlWinEventLog:Microsoft-Windows-Sysmon/Operational OR source=Syslog:Linux-Sysmon/Operational)`
windows_alternate_datastream___executable_content_filter	`search *`

windows_alternate_datastream___executable_content_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
T1564.004	NTFS File Attributes	Stealth

Exploitation

DE.CM

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	No

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

Target environment must ingest Sysmon data, specifically Event ID 15, and import hashing/imphash must be enabled within Sysmon.

Known False Positives

No false positives have been identified at this time.

Associated Analytic Story

Windows Defense Evasion Tactics

Finding

Title	Entity Field	Entity Type	Risk Score
Base64 content written to an NTFS alternate data stream in $dest$, see command field for details.	dest	system	50

Threat Objects

Field	Type
file_name	file_name
file_hash	file_hash

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: 13