name: Powershell Creating Thread Mutex
id: 637557ec-ca08-11eb-bd0a-acde48001122
version: 3
date: '2022-05-02'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic identifies suspicious PowerShell script execution
  via EventCode 4104 that is using the `mutex` function. This function is commonly
  seen in some obfuscated PowerShell scripts to make sure that only one instance of
  there process is running on a compromise machine. During triage, review parallel
  processes within the same timeframe. Review the full script block to identify other
  related artifacts.
data_source:
- Powershell 4104
search: '`powershell` EventCode=4104 ScriptBlockText = "*Threading.Mutex*" | stats
  count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText
  Computer UserID | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
  | `powershell_creating_thread_mutex_filter`'
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 developer may used this function in their script
  for instance checking too.
references:
- https://isc.sans.edu/forums/diary/Some+Powershell+Malicious+Code/22988/
- 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/
tags:
  analytic_story:
  - Malicious PowerShell
  asset_type: Endpoint
  confidence: 80
  impact: 50
  message: A suspicious powershell script contains Thread Mutex in $ScriptBlockText$
    with EventCode $EventCode$ in host $Computer$
  mitre_attack_id:
  - T1027
  - T1027.005
  - T1059.001
  observable:
  - name: Computer
    type: Hostname
    role:
    - Victim
  - name: UserID
    type: User
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - EventCode
  - ScriptBlockText
  - Computer
  - UserID
  risk_score: 40
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/powershell_script_block_logging/sbl_xml.log
    source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
    sourcetype: xmlwineventlog