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Elastic Docs ›Elastic Security Solution [7.16] ›Detections and alerts ›Prebuilt rule reference

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.*
  • 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
  • Initial Access

Version: 1

Added (Elastic Stack release): 7.12.0

Rule authors: Elastic, Austin Songer

Rule license: Elastic License v2

Potential false positives

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Legitimate processes may be spawned from the Microsoft Exchange Server Unified Messaging (UM) service. If known processes are causing false positives, they can be exempted from the rule.

Rule query

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process where event.type == "start" and process.parent.name :
("UMService.exe", "UMWorkerProcess.exe") and not process.name :
("werfault.exe", "wermgr.exe")

Threat mapping

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Framework: MITRE ATT&CKTM

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