---
title: "PowerShell Loading DotNET into Memory via System Reflection Assembly"
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 utilizes PowerShell Script Block Logging (EventCode=4104) to identify suspicious PowerShell execution. Script Block Logging captures the command sent to PowerShell, the full command to be executed. Upon enabling, logs will output to Windows event logs. Dependent upon volume, enable no critical endpoints or all. \
This analytic identifies the use of PowerShell loading .net assembly via reflection. This is commonly found in malicious PowerShell usage, including Empire and Cobalt Strike. In addition, the `load(` value may be modifed by removing `(` and it will identify more events to review. \
During triage, review parallel processes using an EDR product or 4688 events. It will be important to understand the timeline of events around this activity. Review the entire logged PowerShell script block.

- **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**: Michael Haag, Splunk
- **ID**: 85bc3f30-ca28-11eb-bd21-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 IN ("*[system.reflection.assembly]::load(*","*[reflection.assembly]*") 
| stats count min(_time) as firstTime max(_time) as lastTime by OpCode ComputerName User EventCode Message 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `powershell_loading_dotnet_into_memory_via_system_reflection_assembly_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_loading_dotnet_into_memory_via_system_reflection_assembly_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
* Message
* OpCode
* ComputerName
* User
* EventCode


#### 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
False positives should be limited as day to day scripts do not use this method.

#### Associated Analytic story
* [Malicious PowerShell](/stories/malicious_powershell)


#### Kill Chain Phase
* Exploitation



#### RBA

| Risk Score  | Impact      | Confidence   | Message      |
| ----------- | ----------- |--------------|--------------|
| 56.0 | 70 | 80 | A suspicious powershell script contains reflective class assembly  command in $Message$ to load .net code in memory with EventCode $EventCode$ in host $ComputerName$ |


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



#### Reference

* [https://docs.microsoft.com/en-us/dotnet/api/system.reflection.assembly?view=net-5.0](https://docs.microsoft.com/en-us/dotnet/api/system.reflection.assembly?view=net-5.0)
* [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/attack_techniques/T1059.001/powershell_script_block_logging/windows-powershell.log](https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/powershell_script_block_logging/windows-powershell.log)



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