---
title: "Powershell Processing Stream Of Data"
excerpt: "Command and Scripting Interpreter, PowerShell"
categories:
  - Endpoint
last_modified_at: 2021-06-10
toc: true
toc_label: ""
tags:
  - Command and Scripting Interpreter
  - Execution
  - PowerShell
  - Execution
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
---



[Try in Splunk Security Cloud](https://www.splunk.com/en_us/cyber-security.html){: .btn .btn--success}

#### Description

The following analytic identifies suspicious PowerShell script execution via EventCode 4104 that is processing compressed stream data. This is typically found in obfuscated PowerShell or PowerShell executing embedded .NET or binary files that are stream flattened and will be deflated durnig execution. During triage, review parallel processes within the same timeframe. Review the full script block to identify other related artifacts.

- **Type**: [TTP](https://github.com/splunk/security_content/wiki/Detection-Analytic-Types)
- **Product**: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- **Datamodel**: 
- **Last Updated**: 2021-06-10
- **Author**: Teoderick Contreras, Splunk
- **ID**: 0d718b52-c9f1-11eb-bc61-acde48001122


#### [ATT&CK](https://attack.mitre.org/)

| ID             | Technique        |  Tactic             |
| -------------- | ---------------- |-------------------- |
| [T1059](https://attack.mitre.org/techniques/T1059/) | Command and Scripting Interpreter | Execution |

| [T1059.001](https://attack.mitre.org/techniques/T1059/001/) | PowerShell | Execution |

#### Search

```
`powershell` EventCode=4104 Message = "*IO.Compression.*" OR Message = "*IO.StreamReader*" OR Message = "*]::Decompress*" 
| stats count min(_time) as firstTime max(_time) as lastTime by EventCode Message ComputerName User 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `powershell_processing_stream_of_data_filter`
```

#### Macros
The SPL above uses the following Macros:
* [powershell](https://github.com/splunk/security_content/blob/develop/macros/powershell.yml)
* [security_content_ctime](https://github.com/splunk/security_content/blob/develop/macros/security_content_ctime.yml)

Note that `powershell_processing_stream_of_data_filter` is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

#### Required field
* _time
* EventCode
* Message
* ComputerName
* User
* Score


#### How To Implement
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
* [Malicious PowerShell](/stories/malicious_powershell)


#### Kill Chain Phase
* Exploitation



#### RBA

| Risk Score  | Impact      | Confidence   | Message      |
| ----------- | ----------- |--------------|--------------|
| 40.0 | 50 | 80 | A suspicious powershell script contains stream command in $Message$ commonly for processing compressed or to decompressed binary file with EventCode $EventCode$ in host $ComputerName$ |


Note that risk score is calculated base on the following formula: `(Impact * Confidence)/100`



#### Reference

* [https://medium.com/@ahmedjouini99/deobfuscating-emotets-powershell-payload-e39fb116f7b9](https://medium.com/@ahmedjouini99/deobfuscating-emotets-powershell-payload-e39fb116f7b9)
* [https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell](https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell)
* [https://blog.palantir.com/tampering-with-windows-event-tracing-background-offense-and-defense-4be7ac62ac63](https://blog.palantir.com/tampering-with-windows-event-tracing-background-offense-and-defense-4be7ac62ac63)
* [https://static1.squarespace.com/static/552092d5e4b0661088167e5c/t/59c1814829f18782e24f1fe2/1505853768977/Windows+PowerShell+Logging+Cheat+Sheet+ver+Sept+2017+v2.1.pdf](https://static1.squarespace.com/static/552092d5e4b0661088167e5c/t/59c1814829f18782e24f1fe2/1505853768977/Windows+PowerShell+Logging+Cheat+Sheet+ver+Sept+2017+v2.1.pdf)
* [https://www.crowdstrike.com/blog/investigating-powershell-command-and-script-logging/](https://www.crowdstrike.com/blog/investigating-powershell-command-and-script-logging/)



#### Test Dataset
Replay any dataset to Splunk Enterprise by using our [`replay.py`](https://github.com/splunk/attack_data#using-replaypy) tool or the [UI](https://github.com/splunk/attack_data#using-ui).
Alternatively you can replay a dataset into a [Splunk Attack Range](https://github.com/splunk/attack_range#replay-dumps-into-attack-range-splunk-server)

* [https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/honeypots/pwsh/windows-powershell.log](https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/honeypots/pwsh/windows-powershell.log)



[*source*](https://github.com/splunk/security_content/tree/develop/detections/endpoint/powershell_processing_stream_of_data.yml) \| *version*: **1**