name: Powershell Creating Thread Mutex
id: 637557ec-ca08-11eb-bd0a-acde48001122
version: 1
date: '2021-06-10'
author: Teoderick Contreras, Splunk
type: TTP
datamodel: []
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.
search: '`powershell` EventCode=4104 Message = "*Threading.Mutex*" | stats count min(_time)
  as firstTime max(_time) as lastTime by EventCode Message ComputerName User | `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
  automated_detection_testing: passed
  confidence: 80
  context:
  - source:endpoint
  - stage: Defense Evasion
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/honeypots/pwsh/windows-powershell.log
  impact: 50
  kill_chain_phases:
  - Exploitation
  message: A suspicious powershell script contains Thread Mutex in $Message$ with
    EventCode $EventCode$ in host $ComputerName$
  mitre_attack_id:
  - T1027.005
  observable:
  - name: ComputerName
    type: Hostname
    role:
    - Victim
  - name: User
    type: User
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - EventCode
  - Message
  - ComputerName
  - User
  risk_score: 40
  security_domain: endpoint