DLL Execution via Rasautou.exe — Sigma Rule

Rule metadata and linked tags

Author: Julia Fomina, oscd.community. Source status: test; severity: medium. Source dates: 2020-10-09 / not supplied.

{
  "product": "windows",
  "category": "process_creation",
  "definition": "Since options '-d' and '-p' were removed in Windows 10 this rule is relevant only for Windows before 10. And as Windows 7 doesn't log command line in 4688 by default, to detect this attack you need Sysmon 1 configured or KB3004375 installed for command-line auditing (https://support.microsoft.com/en-au/help/3004375/microsoft-security-advisory-update-to-improve-windows-command-line-aud)"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: ffec4d88b229ead277eaf05bc0767607da7fd8dbbf1e8f227d3926f37905e1f6

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: DLL Execution via Rasautou.exe
id: cd3d1298-eb3b-476c-ac67-12847de55813
status: test
description: Detects using Rasautou.exe for loading arbitrary .DLL specified in -d option and executes the export specified in -p.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Rasautou/
    - https://github.com/fireeye/DueDLLigence
    - https://www.fireeye.com/blog/threat-research/2019/10/staying-hidden-on-the-endpoint-evading-detection-with-shellcode.html
author: Julia Fomina, oscd.community
date: 2020-10-09
tags:
    - attack.stealth
    - attack.t1218
logsource:
    product: windows
    category: process_creation
    definition: Since options '-d' and '-p' were removed in Windows 10 this rule is relevant only for Windows before 10. And as Windows 7 doesn't log command line in 4688 by default, to detect this attack you need Sysmon 1 configured or KB3004375 installed for command-line auditing (https://support.microsoft.com/en-au/help/3004375/microsoft-security-advisory-update-to-improve-windows-command-line-aud)
detection:
    selection_img:
        - Image|endswith: '\rasautou.exe'
        - OriginalFileName: 'rasdlui.exe'
    selection_cli:
        CommandLine|contains|all:
            - ' -d '
            - ' -p '
    condition: all of selection*
falsepositives:
    - Unlikely
level: medium

Original YAML and metadata in JSON

False positives

• Unlikely

Source references

• https://lolbas-project.github.io/lolbas/Binaries/Rasautou/
• https://github.com/fireeye/DueDLLigence
• https://www.fireeye.com/blog/threat-research/2019/10/staying-hidden-on-the-endpoint-evading-detection-with-shellcode.html