Suspicious File Encoded To Base64 Through Certutil.EXE (via process_creation)

title: Suspicious File Encoded To Base64 Through Certutil.EXE (via process_creation)
id: 3dca9502-bc6e-51e4-bd22-4af2aa3c217d
status: stable
description: This rule detects the execution of certutil with the "encode" flag to encode a file to base64. This can be misused by threat actors and adversaries for data exfiltration
references:
    - https://attack.mitre.org/techniques/T1027/
    - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/certutil
    - https://unit42.paloaltonetworks.com/new-babyshark-malware-targets-u-s-national-security-think-tanks/
    - https://lolbas-project.github.io/lolbas/Binaries/Certutil/
author: Huntrule Team
date: 2026-06-02
tags:
    - attack.stealth
    - attack.t1027
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\certutil.exe'
        - OriginalFileName: 'CertUtil.exe'
    selection_cli:
        CommandLine|contains|windash: '-encode'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_certutil_encode/info.yml