Dynamic CSharp Compile Artefact

When C# is compiled dynamically, a .cmdline file will be created as a part of the process. Certain processes are not typically observed compiling C# code, but can do so without touching disk. This can be used to unpack a payload for execution

title: Dynamic CSharp Compile Artefact
id: e4a74e34-ecde-4aab-b2fb-9112dd01aed0
status: test
description: |
    When C# is compiled dynamically, a .cmdline file will be created as a part of the process.
    Certain processes are not typically observed compiling C# code, but can do so without touching disk.
    This can be used to unpack a payload for execution
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027.004/T1027.004.md#atomic-test-2---dynamic-c-compile
author: frack113
date: 2022-01-09
modified: 2023-02-17
tags:
    - attack.stealth
    - attack.t1027.004
logsource:
    product: windows
    category: file_event
detection:
    selection:
        TargetFilename|endswith: '.cmdline'
    condition: selection
falsepositives:
    - Unknown
level: low

• T1027.004Compile After Delivery

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027.004/T1027.004.md#atomic-test-2---dynamic-c-compile↗