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Suspicious Image Load (taskschd.dll) from MS Office

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Suspicious Image Load (taskschd.dll) from MS Office

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Identifies a suspicious image load (taskschd.dll) from Microsoft Office processes. This behavior may indicate adversarial activity where a scheduled task is configured via Windows Component Object Model (COM). This technique can be used to configure persistence and evade monitoring by avoiding the usage of the traditional Windows binary (schtasks.exe) used to manage scheduled tasks.

Rule type: eql

Rule indices:

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

Severity: low

Risk score: 21

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: 4 (version history)

Added (Elastic Stack release): 7.11.0

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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library where process.name : ("WINWORD.EXE", "EXCEL.EXE",
"POWERPNT.EXE", "MSPUB.EXE", "MSACCESS.EXE") and event.action :
"load" and event.category : "library" and dll.name :
"taskschd.dll"

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 4 (8.2.0 release)
  • Formatting only
Version 3 (7.12.0 release)

  • Updated query, changed from:

    library where process.name in ("WINWORD.EXE", "EXCEL.EXE",
"POWERPNT.EXE", "MSPUB.EXE", "MSACCESS.EXE") and event.action ==
"load" and event.category == "library" and file.name ==
"taskschd.dll"
Version 2 (7.11.2 release)
  • Formatting only
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