malicious_powershell_process___encoded_command.yml

name: Malicious PowerShell Process - Encoded Command
id: c4db14d9-7909-48b4-a054-aa14d89dbb19
version: 7
date: '2022-01-18'
author: David Dorsey, Michael Haag, Splunk
status: production
type: Hunting
description: 'The following analytic identifies the use of the EncodedCommand PowerShell
  parameter. This is typically used by Administrators to run complex scripts, but
  commonly used by adversaries to hide their code. \

  The analytic identifies all variations of EncodedCommand, as PowerShell allows the
  ability to shorten the parameter. For example enc, enco, encod and so forth. In
  addition, through our research it was identified that PowerShell will interpret
  different command switch types beyond the hyphen. We have added endash, emdash,
  horizontal bar, and forward slash. \

  During triage, review parallel events to determine legitimacy. Tune as needed based
  on admin scripts in use. \

  Alternatively, may use regex per matching here https://regexr.com/662ov.'
data_source:
- Sysmon Event ID 1
search: "| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)\
  \ as lastTime from datamodel=Endpoint.Processes where `process_powershell` by Processes.user\
  \ Processes.process_name Processes.process Processes.parent_process_name Processes.original_file_name\
  \ Processes.dest Processes.process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`\
  \ | `security_content_ctime(lastTime)` | where match(process,\"(?i)[\\-|\\/|\u2013\
  |\u2014|\u2015]e(nc*o*d*e*d*c*o*m*m*a*n*d*)*\\s+[^-]\") | `malicious_powershell_process___encoded_command_filter`"
how_to_implement: The detection is based on data that originates from Endpoint Detection
  and Response (EDR) agents. These agents are designed to provide security-related
  telemetry from the endpoints where the agent is installed. To implement this search,
  you must ingest logs that contain the process GUID, process name, and parent process.
  Additionally, you must ingest complete command-line executions. These logs must
  be processed using the appropriate Splunk Technology Add-ons that are specific to
  the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
  data model. Use the Splunk Common Information Model (CIM) to normalize the field
  names and speed up the data modeling process.
known_false_positives: System administrators may use this option, but it's not common.
references:
- https://regexr.com/662ov
- https://github.com/redcanaryco/AtomicTestHarnesses/blob/master/TestHarnesses/T1059.001_PowerShell/OutPowerShellCommandLineParameter.ps1
- https://ss64.com/ps/powershell.html
- https://twitter.com/M_haggis/status/1440758396534214658?s=20
- https://www.microsoft.com/security/blog/2022/01/15/destructive-malware-targeting-ukrainian-organizations/
- https://www.microsoft.com/en-us/security/blog/2023/05/24/volt-typhoon-targets-us-critical-infrastructure-with-living-off-the-land-techniques/
tags:
  analytic_story:
  - Hermetic Wiper
  - Malicious PowerShell
  - NOBELIUM Group
  - WhisperGate
  - DarkCrystal RAT
  - Qakbot
  - CISA AA22-320A
  - Sandworm Tools
  - Data Destruction
  - Volt Typhoon
  asset_type: Endpoint
  confidence: 50
  impact: 70
  message: Powershell.exe running potentially malicious encodede commands on $dest$
  mitre_attack_id:
  - T1027
  observable:
  - name: dest
    type: Endpoint
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.process_name
  - Processes.process
  - Processes.user
  - Processes.parent_process_name
  - Processes.dest
  - Processes.process_id
  risk_score: 35
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1027/atomic_red_team/windows-sysmon.log
    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
    sourcetype: xmlwineventlog