Suspicious Spool Service Child Process

detection:
  spoolsv:
    IntegrityLevel:
      - 'System'
      - 'S-1-16-16384'
    ParentImage|endswith: '\spoolsv.exe'
  suspicious_cmd:
    Image|endswith: '\cmd.exe'
  suspicious_cmd_filter:
    CommandLine|contains:
      - '.spl'
      - 'route add'
      - 'program files'
  suspicious_net:
    Image|endswith:
      - '\net.exe'
      - '\net1.exe'
  suspicious_net_filter:
    CommandLine|contains: 'start'
  suspicious_netsh:
    Image|endswith: '\netsh.exe'
  suspicious_netsh_filter:
    CommandLine|contains:
      - 'add portopening'
      - 'rule name'
  suspicious_powershell:
    Image|endswith:
      - '\powershell.exe'
      - '\pwsh.exe'
  suspicious_powershell_filter:
    CommandLine|contains: '.spl'
  suspicious_rundll32_cli:
    CommandLine|endswith: 'rundll32.exe'
  suspicious_rundll32_img:
    - Image|endswith: '\rundll32.exe'
    - OriginalFileName: 'RUNDLL32.EXE'
  suspicious_unrestricted:
    Image|endswith:
      - '\gpupdate.exe'
      - '\whoami.exe'
      - '\nltest.exe'
      - '\taskkill.exe'
      - '\wmic.exe'
      - '\taskmgr.exe'
      - '\sc.exe'
      - '\findstr.exe'
      - '\curl.exe'
      - '\wget.exe'
      - '\certutil.exe'
      - '\bitsadmin.exe'
      - '\accesschk.exe'
      - '\wevtutil.exe'
      - '\bcdedit.exe'
      - '\fsutil.exe'
      - '\cipher.exe'
      - '\schtasks.exe'
      - '\write.exe'
      - '\wuauclt.exe'
      - '\systeminfo.exe'
      - '\reg.exe'
      - '\query.exe'
  condition: spoolsv and ( suspicious_unrestricted or (suspicious_net and not suspicious_net_filter) or (suspicious_cmd and not suspicious_cmd_filter) or (suspicious_netsh and not suspicious_netsh_filter) or (suspicious_powershell and not suspicious_powershell_filter) or all of suspicious_rundll32_* )

The rule’s detection, its selections and fields in order of name. The whole rule, with its references and false positives, is on SigmaHQ, by Justin C. (@endisphotic), @dreadphones (detection), Thomas Patzke (Sigma rule), under the Detection Rule License 1.1. CmdID evaluates it on a command line alone: a test on what a command line cannot show, such as the parent process or the user, is not met.

None of the everyday examples and documented commands on CmdID’s program pages trips it. To see whether a command line does, paste it into CmdID.