title: Suspicious Certutil Command
status: experimental
description: Detetcs a suspicious Microsoft certutil execution with sub commands like 'decode' sub command, which is sometimes used to decode malicious code with the built-in certutil utility
author:
    - Florian Roth
    - juju4
reference: 
    - https://twitter.com/JohnLaTwC/status/835149808817991680
    - https://twitter.com/subTee/status/888102593838362624
    - https://twitter.com/subTee/status/888071631528235010
    - https://blogs.technet.microsoft.com/pki/2006/11/30/basic-crl-checking-with-certutil/
    - https://www.trustedsec.com/2017/07/new-tool-release-nps_payload/
logsource:
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 1
        CommandLine: 
            - '*\certutil.exe * -decode *'
            - '*\certutil.exe * -decodehex *'
            - '*\certutil.exe *-urlcache* http*'
            - '*\certutil.exe *-urlcache* ftp*'
            - '*\certutil.exe *-URL*'
            - '*\certutil.exe *-ping*'
    condition: selection
falsepositives:
    - False positives depend on scripts and administrative tools used in the monitored environment
level: high