Detection: Windows Alternate DataStream - Process Execution

Updated Date: 2024-05-16 ID: 30c32c5c-41fe-45db-84fe-275e4320da3f Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects when a process attempts to execute a file from within an NTFS file system alternate data stream. This detection leverages process execution data from sources like Windows process monitoring or Sysmon Event ID 1, focusing on specific processes known for such behavior. This activity is significant because alternate data streams can be used by threat actors to hide malicious code, making it difficult to detect. If confirmed malicious, this could allow an attacker to execute hidden code, potentially leading to unauthorized actions and further compromise of the system.

1
2| tstats count min(_time) as firstTime max(_time) as lastTime values(Processes.process_current_directory) as directory from datamodel=Endpoint.Processes where Processes.parent_process_name != "unknown" Processes.process_name IN ("appvlp.exe","bitsadmin.exe","control.exe","cscript.exe","forfiles.exe","ftp.exe","mavinject.exe","mshta.exe","powershell.exe","powershell_ise.exe","pwsh.exe","regini.exe","regscr32.exe","rundll32.exe","sc.exe","wmic.exe","wscript.exe") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| regex process="(\b)\w+(\.\w+)?:\w+(\.\w{2,4})(?!\.)(\b
5|\s
6|&)" 
7| `security_content_ctime(firstTime)` 
8| `security_content_ctime(lastTime)` 
9| `windows_alternate_datastream___process_execution_filter`

Data Source

Name Platform Sourcetype Source Supported App
Sysmon EventID 1 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' N/A

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_alternate_datastream___process_execution_filter search *
windows_alternate_datastream___process_execution_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 Hide Artifacts Defense Evasion
T1564.004 NTFS File Attributes Defense Evasion
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
APT32

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

Target environment must ingest process execution data sources such as Windows process monitoring and/or Sysmon EventID 1.

Known False Positives

False positives may be generated by process executions within the commandline, regex has been provided to minimize the possibilty.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
The $process_name$ process was executed by $user$ using data from an NTFS alternate data stream. 80 100 80
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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: 2