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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 on critical endpoints or all.
This analytic identifies "MSF.Powershell","MSF.Powershell.Meterpreter","MSF.Powershell.Meterpreter.Kiwi","MSF.Powershell.Meterpreter.Transport" being used. This behavior is related to when a Meterpreter session is started and the operator runs load_kiwi.
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

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2022-11-22
  • Author: Michael Haag, Splunk
  • ID: d5905da5-d050-48db-9259-018d8f034fcf

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1059 Command and Scripting Interpreter Execution
T1059.001 PowerShell Execution
Kill Chain Phase
  • Exploitation
NIST
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE 


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`powershell` EventCode=4104 ScriptBlockText IN ("*MSF.Powershell*","*MSF.Powershell.Meterpreter*","*MSF.Powershell.Meterpreter.Kiwi*","*MSF.Powershell.Meterpreter.Transport*") 
| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer user_id 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `powershell_load_module_in_meterpreter_filter`

Macros

The SPL above uses the following Macros:

:information_source: powershell_load_module_in_meterpreter_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • EventCode
  • ScriptBlockText
  • Computer
  • User_id

How To Implement

The following analytic requires PowerShell operational logs to be imported. Modify the powershell macro as needed to match the sourcetype or add index. This analytic is specific to 4104, or PowerShell Script Block Logging.

Known False Positives

False positives should be very limited as this is strict to MetaSploit behavior.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
100.0 100 100 PowerShell was identified running a script utilized by Meterpreter from MetaSploit on endpoint $Computer$ by user $user_id$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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

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