DotNet CLR DLL Loaded By Scripting Applications

Status: test
Severity: high
Log source: category image_load, product windows
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

Tactic	Techniques
Privilege Escalation	`T1055` Process Injection
Stealth	`T1055` Process Injection

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 7: Image loaded

Rule body

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

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\cmstp.exe` corpus 8 (sigma 8) `\cscript.exe` corpus 72 (sigma 72) `\mshta.exe` corpus 66 (sigma 66) `\msxsl.exe` corpus 6 (sigma 6) `\regsvr32.exe` corpus 64 (sigma 64) `\wmic.exe` corpus 62 (sigma 62) `\wscript.exe` corpus 74 (sigma 74)	`field:"Image" kind:ends_with`
`ImageLoaded`	ends_with	`\clr.dll` `\mscoree.dll` corpus 2 (sigma 2) `\mscorlib.dll`	`field:"ImageLoaded" kind:ends_with`