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Detection rules › Sigma

DotNet CLR DLL Loaded By Scripting Applications

Status
test
Severity
high
Log source
product windows, category image_load
Author
omkar72, oscd.community
Source
github.com/SigmaHQ/sigma

Detects .NET CLR DLLs being loaded by scripting applications such as wscript or cscript. This could be an indication of potential suspicious execution.

MITRE ATT&CK coverage

TacticTechniques
Privilege EscalationT1055 Process Injection
StealthT1055 Process Injection

Event coverage

ProviderEventTitle
SysmonEvent ID 7Image loaded

Rule body yaml

title: DotNet CLR DLL Loaded By Scripting Applications
id: 4508a70e-97ef-4300-b62b-ff27992990ea
status: test
description: Detects .NET CLR DLLs being loaded by scripting applications such as wscript or cscript. This could be an indication of potential suspicious execution.
references:
    - https://github.com/tyranid/DotNetToJScript
    - https://thewover.github.io/Introducing-Donut/
    - https://web.archive.org/web/20230329154538/https://blog.menasec.net/2019/07/interesting-difr-traces-of-net-clr.html
    - https://web.archive.org/web/20221026202428/https://gist.github.com/code-scrap/d7f152ffcdb3e0b02f7f394f5187f008
author: omkar72, oscd.community
date: 2020-10-14
modified: 2023-02-23
tags:
    - attack.execution
    - attack.privilege-escalation
    - attack.stealth
    - attack.t1055
logsource:
    category: image_load
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmstp.exe'
            - '\cscript.exe'
            - '\mshta.exe'
            - '\msxsl.exe'
            - '\regsvr32.exe'
            # - '\svchost.exe'
            - '\wmic.exe'
            - '\wscript.exe'
        ImageLoaded|endswith:
            - '\clr.dll'
            - '\mscoree.dll'
            - '\mscorlib.dll'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith:
        - '\cmstp.exe'
        - '\cscript.exe'
        - '\mshta.exe'
        - '\msxsl.exe'
        - '\regsvr32.exe'
        - '\wmic.exe'
        - '\wscript.exe'
    ImageLoaded|endswith:
        - '\clr.dll'
        - '\mscoree.dll'
        - '\mscorlib.dll'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Imageends_with
  • \cmstp.exe corpus 8 (sigma 8)
  • \cscript.exe corpus 73 (sigma 73)
  • \mshta.exe corpus 67 (sigma 67)
  • \msxsl.exe corpus 6 (sigma 6)
  • \regsvr32.exe corpus 65 (sigma 65)
  • \wmic.exe corpus 60 (sigma 60)
  • \wscript.exe corpus 75 (sigma 75)
ImageLoadedends_with
  • \clr.dll
  • \mscoree.dll corpus 2 (sigma 2)
  • \mscorlib.dll