IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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Microsoft Exchange Server UM Spawning Suspicious Processes

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Microsoft Exchange Server UM Spawning Suspicious Processes

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Identifies suspicious processes being spawned by the Microsoft Exchange Server Unified Messaging (UM) service. This activity has been observed exploiting CVE-2021-26857.

Rule type: eql

Rule indices:

logs-endpoint.events.process-*
winlogbeat-*
logs-windows.*
endgame-*
logs-system.security*

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: Initial Access
Tactic: Lateral Movement
Data Source: Elastic Endgame
Use Case: Vulnerability
Data Source: Elastic Defend

Version: 109

Rule authors:

Elastic
Austin Songer

Rule license: Elastic License v2

Setup

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Setup

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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process where host.os.type == "windows" and event.type == "start" and
  process.parent.name : ("UMService.exe", "UMWorkerProcess.exe") and
    not process.executable :
              ("?:\\Windows\\System32\\werfault.exe",
               "?:\\Windows\\System32\\wermgr.exe",
               "?:\\Program Files\\Microsoft\\Exchange Server\\V??\\Bin\\UMWorkerProcess.exe",
               "?:\\Program Files\\Microsoft\\Exchange Server\\Bin\\UMWorkerProcess.exe",
               "D:\\Exchange 2016\\Bin\\UMWorkerProcess.exe",
               "E:\\ExchangeServer\\Bin\\UMWorkerProcess.exe",
               "D:\\Exchange\\Bin\\UMWorkerProcess.exe",
               "D:\\Exchange Server\\Bin\\UMWorkerProcess.exe",
               "E:\\Exchange Server\\V15\\Bin\\UMWorkerProcess.exe")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Initial Access
- ID: TA0001
- Reference URL: https://attack.mitre.org/tactics/TA0001/
Technique:
- Name: Exploit Public-Facing Application
- ID: T1190
- Reference URL: https://attack.mitre.org/techniques/T1190/
Tactic:
- Name: Lateral Movement
- ID: TA0008
- Reference URL: https://attack.mitre.org/tactics/TA0008/
Technique:
- Name: Exploitation of Remote Services
- ID: T1210
- Reference URL: https://attack.mitre.org/techniques/T1210/

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