Legitimate Application Dropped Script — Sigma Rule

Rule metadata and linked tags

Author: frack113, Florian Roth (Nextron Systems). Source status: test; severity: high. Source dates: 2022-08-21 / 2023-06-22.

{
  "product": "windows",
  "category": "file_event"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: c67ce413622fc5feba663acd72cf9cf4e9d58afede3fbf0c266df416530bb460

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Legitimate Application Dropped Script
id: 7d604714-e071-49ff-8726-edeb95a70679
status: test
description: Detects programs on a Windows system that should not write scripts to disk
references:
    - https://github.com/Neo23x0/sysmon-config/blob/3f808d9c022c507aae21a9346afba4a59dd533b9/sysmonconfig-export-block.xml#L1326
author: frack113, Florian Roth (Nextron Systems)
date: 2022-08-21
modified: 2023-06-22
tags:
    - attack.stealth
    - attack.t1218
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith:
            # Microsoft Office Programs Dropping Executables / Rest of the apps are covered in: c7a74c80-ba5a-486e-9974-ab9e682bc5e4
            - \eqnedt32.exe
            - \wordpad.exe
            - \wordview.exe
            # LOLBINs that can be used to download executables
            - \certutil.exe
            - \certoc.exe
            - \CertReq.exe
            # - \bitsadmin.exe (depends on the environment; comment in if you're sure that bitsadmin doesn't do that in your env)
            - \Desktopimgdownldr.exe
            - \esentutl.exe
            # - \expand.exe
            - '\mshta.exe'
            # Executables that should never drop an executable to disk (but may after a previous process injection or if it's malware that uses a legitimate name)
            - '\AcroRd32.exe'
            - '\RdrCEF.exe'
            - '\hh.exe'
            - '\finger.exe'
        TargetFilename|endswith:
            - '.ps1'
            - '.bat'
            - '.vbs'
            - '.scf'
            - '.wsf'
            - '.wsh'
    condition: selection
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://github.com/Neo23x0/sysmon-config/blob/3f808d9c022c507aae21a9346afba4a59dd533b9/sysmonconfig-export-block.xml#L1326