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Encoding or Decoding Files via CertUtil

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IMPORTANT: This documentation is no longer updated. Refer to Elastic's version policy and the latest documentation.

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: query

Rule indices:

winlogbeat-*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum signals per execution: 100

Tags:

Elastic
Windows

Version: 2 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.7.0

Rule query

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

Threat mapping

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Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Deobfuscate/Decode Files or Information
- ID: T1140
- Reference URL: https://attack.mitre.org/techniques/T1140/

Rule version history

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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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