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Elastic Docs ›Elastic Security Solution [7.13] ›Detections and alerts ›Prebuilt rule reference

Encoding or Decoding Files via CertUtil

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Encoding or Decoding Files via CertUtil

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Identifies the use of certutil.exe to encode or decode data. CertUtil is a native Windows component which is part of Certificate Services. CertUtil is often abused by attackers to encode or decode base64 data for stealthier command and control or exfiltration.

Rule type: eql

Rule indices:

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

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Defense Evasion

Version: 8 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.13.0

Rule authors: Elastic

Rule license: Elastic License v2

Rule query

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process where event.type == "start" and (process.name :
"certutil.exe" or process.pe.original_file_name == "CertUtil.exe") and
process.args : ("?decode", "?encode")

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 8 (7.13.0 release)

  • Updated query, changed from:

    event.category:process and event.type:(start or process_started) and
process.name:certutil.exe and process.args:(-decode or -encode or
/decode or /encode)
Version 7 (7.12.0 release)
  • Formatting only
Version 6 (7.11.2 release)
  • Formatting only
Version 5 (7.10.0 release)
  • Formatting only
Version 4 (7.9.1 release)
  • Formatting only
Version 3 (7.9.0 release)

  • Updated query, changed from:

    event.action:"Process Create (rule: ProcessCreate)" and
process.name:certutil.exe and process.args:(-decode or -encode or
/decode or /encode)
Version 2 (7.7.0 release)

  • Updated query, changed from:

    event.action:"Process Create (rule: ProcessCreate)" and
process.name:"certutil.exe" and process.args:("-encode" or "/encode"
or "-decode" or "/decode")
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