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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Elastic Docs ›Elastic Security Solution [8.2] ›Detections and alerts ›Prebuilt rule reference

Microsoft Exchange Worker Spawning Suspicious Processes

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Microsoft Exchange Worker Spawning Suspicious Processes

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Identifies suspicious processes being spawned by the Microsoft Exchange Server worker process (w3wp). This activity may indicate exploitation activity or access to an existing web shell backdoor.

Rule type: eql

Rule indices:

  • logs-endpoint.events.*
  • winlogbeat-*
  • logs-windows.*

Severity: high

Risk score: 73

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: 3 (version history)

Added (Elastic Stack release): 7.12.0

Last modified (Elastic Stack release): 8.2.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guide

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## Config

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 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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process where event.type == "start" and process.parent.name :
"w3wp.exe" and process.parent.args : "MSExchange*AppPool" and
(process.name : ("cmd.exe", "powershell.exe", "pwsh.exe",
"powershell_ise.exe") or process.pe.original_file_name in
("cmd.exe", "powershell.exe", "pwsh.dll", "powershell_ise.exe"))

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 3 (8.2.0 release)
  • Formatting only
Version 2 (7.16.0 release)

  • Updated query, changed from:

    process where event.type == "start" and process.parent.name :
"w3wp.exe" and process.parent.args : "MSExchange*AppPool" and
(process.name : ("cmd.exe", "powershell.exe", "pwsh.exe") or
process.pe.original_file_name : ("cmd.exe", "powershell.exe",
"pwsh.exe"))
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