Use NTFS Short Name in Command Line

Hunt Hypothesis

Detect use of the Windows 8.3 short name. Which could be used as a method to avoid command-line detection

Detection Rule

Sigma (Original)

title: Use NTFS Short Name in Command Line
id: dd6b39d9-d9be-4a3b-8fe0-fe3c6a5c1795
related:
    - id: 3ef5605c-9eb9-47b0-9a71-b727e6aa5c3b
      type: similar
status: test
description: Detect use of the Windows 8.3 short name. Which could be used as a method to avoid command-line detection
references:
    - https://www.acunetix.com/blog/articles/windows-short-8-3-filenames-web-security-problem/
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/cc959352(v=technet.10)
    - https://twitter.com/jonasLyk/status/1555914501802921984
author: frack113, Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-05
modified: 2022-09-21
tags:
    - attack.stealth
    - attack.t1564.004
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains:
            - '~1.exe'
            - '~1.bat'
            - '~1.msi'
            - '~1.vbe'
            - '~1.vbs'
            - '~1.dll'
            - '~1.ps1'
            - '~1.js'
            - '~1.hta'
            - '~2.exe'
            - '~2.bat'
            - '~2.msi'
            - '~2.vbe'
            - '~2.vbs'
            - '~2.dll'
            - '~2.ps1'
            - '~2.js'
            - '~2.hta'
    filter:
        - ParentImage|endswith:
              - '\WebEx\WebexHost.exe'
              - '\thor\thor64.exe'
        - CommandLine|contains: 'C:\xampp\vcredist\VCREDI~1.EXE'
    condition: selection and not filter
falsepositives:
    - Applications could use this notation occasionally which might generate some false positives. In that case Investigate the parent and child process.
level: medium

KQL (Azure Sentinel)

imProcessCreate
| where (TargetProcessCommandLine contains "~1.exe" or TargetProcessCommandLine contains "~1.bat" or TargetProcessCommandLine contains "~1.msi" or TargetProcessCommandLine contains "~1.vbe" or TargetProcessCommandLine contains "~1.vbs" or TargetProcessCommandLine contains "~1.dll" or TargetProcessCommandLine contains "~1.ps1" or TargetProcessCommandLine contains "~1.js" or TargetProcessCommandLine contains "~1.hta" or TargetProcessCommandLine contains "~2.exe" or TargetProcessCommandLine contains "~2.bat" or TargetProcessCommandLine contains "~2.msi" or TargetProcessCommandLine contains "~2.vbe" or TargetProcessCommandLine contains "~2.vbs" or TargetProcessCommandLine contains "~2.dll" or TargetProcessCommandLine contains "~2.ps1" or TargetProcessCommandLine contains "~2.js" or TargetProcessCommandLine contains "~2.hta") and (not((((ParentProcessName endswith "\\WebEx\\WebexHost.exe" or ParentProcessName endswith "\\thor\\thor64.exe") or (ActingProcessName endswith "\\WebEx\\WebexHost.exe" or ActingProcessName endswith "\\thor\\thor64.exe")) or TargetProcessCommandLine contains "C:\\xampp\\vcredist\\VCREDI~1.EXE")))

Required Data Sources

False Positive Guidance

• Applications could use this notation occasionally which might generate some false positives. In that case Investigate the parent and child process.

MITRE ATT&CK Context

• Technique: T1564.004 — T1564.004

References

• https://www.acunetix.com/blog/articles/windows-short-8-3-filenames-web-security-problem/
• https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/cc959352(v=technet.10)
• https://twitter.com/jonasLyk/status/1555914501802921984
• SigmaHQ Rule