New ActiveSyncAllowedDeviceID Added via PowerShell

Identifies the use of the Exchange PowerShell cmdlet, Set-CASMailbox, to add a new ActiveSync allowed device. Adversaries may target user email to collect sensitive information.

Rule type: eql

Rule indices:

logs-endpoint.events.process-*
winlogbeat-*
logs-windows.forwarded*
logs-windows.sysmon_operational-*
endgame-*
logs-system.security*
logs-m365_defender.event-*
logs-sentinel_one_cloud_funnel.*
logs-crowdstrike.fdr*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Persistence
Tactic: Execution
Data Source: Elastic Endgame
Data Source: Elastic Defend
Data Source: System
Data Source: Microsoft Defender for Endpoint
Data Source: Sysmon
Data Source: SentinelOne
Data Source: Crowdstrike

Version: 311

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

process where host.os.type == "windows" and event.type == "start" and
  process.name: ("powershell.exe", "pwsh.exe", "powershell_ise.exe") and process.args : "Set-CASMailbox*ActiveSyncAllowedDeviceIDs*"

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Account Manipulation
- ID: T1098
- Reference URL: https://attack.mitre.org/techniques/T1098/
Sub-technique:
- Name: Additional Email Delegate Permissions
- ID: T1098.002
- Reference URL: https://attack.mitre.org/techniques/T1098/002/
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/

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