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.*
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
Persistence

Version: 6 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 7.16.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Legitimate exchange system administration activity.

Rule query

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

Threat mapping

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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/

Rule version history

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Version 6 (7.16.0 release)

Updated query, changed from:

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

Version 4 (7.15.0 release)

Formatting only

Version 3 (7.12.0 release)

Formatting only

Version 2 (7.11.2 release)

Formatting only

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