Detect Mimikatz With PowerShell Script Block Logging

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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 no critical endpoints or all.
This analytic identifies common Mimikatz functions that may be identified in the script block, including mimikatz. This will catch the most basic use cases for Pass the Ticket, Pass the Hash and -DumprCreds.
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: 2022-02-24
• Author: Michael Haag, Splunk
• ID: 8148c29c-c952-11eb-9255-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1003	OS Credential Dumping	Credential Access

T1059.001

PowerShell

Execution

Kill Chain Phase

• Exploitation
• Installation

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

`powershell` EventCode=4104 ScriptBlockText IN (*mimikatz*, *-dumpcr*, *sekurlsa::pth*, *kerberos::ptt*, *kerberos::golden*) 
| stats count min(_time) as firstTime max(_time) as lastTime by Opcode Computer UserID EventCode ScriptBlockText 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `detect_mimikatz_with_powershell_script_block_logging_filter`

Macros

The SPL above uses the following Macros:

• powershell
• security_content_ctime

detect_mimikatz_with_powershell_script_block_logging_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
• ScriptBlockText
• Opcode
• Computer
• UserID
• 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 the commands being identifies are quite specific to EventCode 4104 and Mimikatz. Filter as needed.

Associated Analytic Story

• Hermetic Wiper
• Malicious PowerShell
• CISA AA22-264A
• CISA AA22-320A
• Sandworm Tools
• Data Destruction

RBA

Risk Score	Impact	Confidence	Message
90.0	90	100	The following behavior was identified and typically related to MimiKatz being loaded within the context of PowerShell on $Computer$ by $UserID$.

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

• 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://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.splunk.com/en_us/blog/security/hunting-for-malicious-powershell-using-script-block-logging.html

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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