New ActiveSyncAllowedDeviceID Added via PowerShell

Elastic Stack Serverless Security

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.*
• winlogbeat-*
• logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (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:

• https://www.volexity.com/blog/2020/12/14/dark-halo-leverages-solarwinds-compromise-to-breach-organizations/
• https://docs.microsoft.com/en-us/powershell/module/exchange/set-casmailbox?view=exchange-ps

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Collection

Version: 4

Rule authors:

• Elastic

Rule license: Elastic License v2

process where event.type in ("start", "process_started") and
  process.name: ("powershell.exe", "pwsh.exe") and process.args : "Set-CASMailbox*ActiveSyncAllowedDeviceIDs*"

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Collection
  • ID: TA0009
  • Reference URL: https://attack.mitre.org/tactics/TA0009/

• Technique:

  • Name: Email Collection
  • ID: T1114
  • Reference URL: https://attack.mitre.org/techniques/T1114/

• Technique:

  • Name: Data from Local System
  • ID: T1005
  • Reference URL: https://attack.mitre.org/techniques/T1005/