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Dynamic CSharp Compile Artefact — Sigma Rule

Sigma rule e4a74e34-ecde-4aab-b2fb-9112dd01aed0. Dynamic CSharp Compile Artefact — Sigma Rule. 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

Rule metadata and linked tags

testlowwindowsfile_eventattack.stealthattack.t1027.004

Author: frack113. Source status: test; severity: low. Source dates: 2022-01-09 / 2023-02-17.

{
  "product": "windows",
  "category": "file_event"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 5f29bfc04d27f5cee70d70d1edf513c2709d8b2e70e18ebf6bd241208ce7eb70

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: 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

Original YAML and metadata in JSON

False positives

  • Unknown

Source references

Connected ecosystem references

Exact source-tagged techniques

Telemetry review

Read the original logsource above, then inspect the linked detection workspaces for technique-level sensor context. No per-rule telemetry equivalence is inferred.

Pinned research references. No browser attack runner, live simulation result or validated detector is asserted. Source mappings and validation limits are preserved. ATT&CK / Atomic provenance · Detection provenance.