Microsoft Exchange Transport Agent Install Script

Elastic Stack Serverless Security

Identifies the use of Cmdlets and methods related to Microsoft Exchange Transport Agents install. Adversaries may leverage malicious Microsoft Exchange Transport Agents to execute tasks in response to adversary-defined criteria, establishing persistence.

Rule type: query

Rule indices:

• winlogbeat-*
• logs-windows.powershell*

Severity: low

Risk score: 21

Runs every: 60m

Searches indices from: now-119m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

• Domain: Endpoint
• OS: Windows
• Use Case: Threat Detection
• Tactic: Persistence
• Data Source: PowerShell Logs
• Rule Type: BBR

Version: 107

Rule authors:

• Elastic

Rule license: Elastic License v2

Setup

The PowerShell Script Block Logging logging policy must be enabled. Steps to implement the logging policy with Advanced Audit Configuration:

Computer Configuration >
Administrative Templates >
Windows PowerShell >
Turn on PowerShell Script Block Logging (Enable)

Steps to implement the logging policy via registry:

reg add "hklm\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging" /v EnableScriptBlockLogging /t REG_DWORD /d 1

event.category: "process" and host.os.type:windows and
  powershell.file.script_block_text : (
    (
    "Install-TransportAgent" or
    "Enable-TransportAgent"
    )
  ) and
  not user.id : "S-1-5-18" and
  not powershell.file.script_block_text : (
    "'Install-TransportAgent', 'Invoke-MonitoringProbe', 'Mount-Database', 'Move-ActiveMailboxDatabase'," or
    "'Enable-TransportAgent', 'Enable-TransportRule', 'Export-ActiveSyncLog', 'Export-AutoDiscoverConfig'," or
    ("scriptCmd.GetSteppablePipeline" and "ForwardHelpTargetName Install-TransportAgent")
  )

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Persistence
  • ID: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Server Software Component
  • ID: T1505
  • Reference URL: https://attack.mitre.org/techniques/T1505/

• Sub-technique:

  • Name: Transport Agent
  • ID: T1505.002
  • Reference URL: https://attack.mitre.org/techniques/T1505/002/

• Tactic:

  • Name: Execution
  • ID: TA0002
  • Reference URL: https://attack.mitre.org/tactics/TA0002/

• Technique:

  • Name: Command and Scripting Interpreter
  • ID: T1059
  • Reference URL: https://attack.mitre.org/techniques/T1059/

• Sub-technique:

  • Name: PowerShell
  • ID: T1059.001
  • Reference URL: https://attack.mitre.org/techniques/T1059/001/