Detection: Powershell Processing Stream Of Data

Updated Date: 2024-11-22 ID: 0d718b52-c9f1-11eb-bc61-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects suspicious PowerShell script execution involving compressed stream data processing, identified via EventCode 4104. It leverages PowerShell Script Block Logging to flag scripts using IO.Compression, IO.StreamReader, or decompression methods. This activity is significant as it often indicates obfuscated PowerShell or embedded .NET/binary execution, which are common tactics for evading detection. If confirmed malicious, this behavior could allow attackers to execute hidden code, escalate privileges, or maintain persistence within the environment.

Search

1`powershell` EventCode=4104 ScriptBlockText = "*IO.Compression.*" OR ScriptBlockText = "*IO.StreamReader*" OR ScriptBlockText = "*]::Decompress*" 
2| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID 
3| rename UserID as user 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `powershell_processing_stream_of_data_filter`

Data Source

Name	Platform	Sourcetype	Source
Powershell Script Block Logging 4104	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'`

Macros Used

Name	Value
powershell	`(source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")`
powershell_processing_stream_of_data_filter	`search *`

powershell_processing_stream_of_data_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
T1059	Command and Scripting Interpreter	Execution
T1059.001	PowerShell	Execution

Installation

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 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

To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

powershell may used this function to process compressed data.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

A suspicious powershell script contains stream command in $ScriptBlockText$ commonly for processing compressed or to decompressed binary file with EventCode $EventCode$ in host $Computer$

Risk Object	Risk Object Type	Risk Score	Threat Objects
user	user	40	No Threat Objects
Computer	system	40	No Threat Objects

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/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: 6