New ActiveSyncAllowedDeviceID Added via PowerShelledit

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: 5 minutes

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

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Collection

Version: 3 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 7.12.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positivesedit

Legitimate exchange system administration activity.

Rule queryedit

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

Threat mappingedit

Framework: MITRE ATT&CKTM

Rule version historyedit

Version 3 (7.12.0 release)
  • Formatting only
Version 2 (7.11.2 release)
  • Formatting only