ID | Technique | Tactic |
---|---|---|
T1059 | Command and Scripting Interpreter | Execution |
T1059.001 | PowerShell | Execution |
Detection: PowerShell Loading DotNET into Memory via Reflection
Description
The following analytic detects the use of PowerShell to load .NET assemblies into memory via reflection, a technique often used in malicious activities such as those by Empire and Cobalt Strike. It leverages PowerShell Script Block Logging (EventCode=4104) to capture and analyze the full command executed. This behavior is significant as it can indicate advanced attack techniques aiming to execute code in memory, bypassing traditional defenses. If confirmed malicious, this activity could lead to unauthorized code execution, privilege escalation, and persistent access within the environment.
Search
1`powershell` EventCode=4104 ScriptBlockText IN ("*[system.reflection.assembly]::load(*","*[reflection.assembly]*", "*reflection.assembly*")
2| stats count min(_time) as firstTime max(_time) as lastTime by Opcode Computer UserID EventCode ScriptBlockText
3| `security_content_ctime(firstTime)`
4| `security_content_ctime(lastTime)`
5| `powershell_loading_dotnet_into_memory_via_reflection_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_loading_dotnet_into_memory_via_reflection_filter | search * |
powershell_loading_dotnet_into_memory_via_reflection_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 |
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
False positives should be limited as day to day scripts do not use this method.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A suspicious powershell script contains reflective class assembly command in $ScriptBlockText$ to load .net code in memory with EventCode $EventCode$ in host $Computer$ | 56 | 70 | 80 |
References
-
https://docs.microsoft.com/en-us/dotnet/api/system.reflection.assembly?view=net-5.0
-
https://www.crowdstrike.com/blog/investigating-powershell-command-and-script-logging/
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: 5