Microsoft Exchange Server UM Spawning Suspicious Processes

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.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: Initial Access
Tactic: Lateral Movement
Data Source: Elastic Endgame
Use Case: Vulnerability
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
Austin Songer

Rule license: Elastic License v2

Rule query

edit

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",
          "\\Device\\HarddiskVolume?\\Windows\\System32\\werfault.exe",
          "\\Device\\HarddiskVolume?\\Windows\\System32\\wermgr.exe",
          "\\Device\\HarddiskVolume?\\Program Files\\Microsoft\\Exchange Server\\V??\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Program Files\\Microsoft\\Exchange Server\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange 2016\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\ExchangeServer\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange Server\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\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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