Assembly DLL Creation Via AspNetCompiler

Description

Detects the creation of new DLL assembly files by "aspnet_compiler.exe", which could be a sign of "aspnet_compiler" abuse to proxy execution through a build provider.

Query · sigma

selection:
  Image|endswith: \aspnet_compiler.exe
  TargetFilename|contains|all:
  - \Temporary ASP.NET Files\
  - \assembly\tmp\
  - .dll
condition: selection

Known false positives

  • Legitimate assembly compilation using a build provider
Raw source Assembly DLL Creation Via AspNetCompiler · Sigma
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Published by SigmaHQ/sigma ↗, licensed under Detection Rule License 1.1 ↗. Reproduced here unmodified. 
title: Assembly DLL Creation Via AspNetCompiler
id: 4c7f49ee-2638-43bb-b85b-ce676c30b260 # TMP File
related:
    - id: 9ccba514-7cb6-4c5c-b377-700758f2f120 # SuspChild
      type: similar
    - id: 9f50fe98-fe5c-4a2d-86c7-fad7f63ed622 # Susp Paths
      type: similar
    - id: a01b8329-5953-4f73-ae2d-aa01e1f35f00 # Exec
      type: similar
status: test
description: |
    Detects the creation of new DLL assembly files by "aspnet_compiler.exe", which could be a sign of "aspnet_compiler" abuse to proxy execution through a build provider.
references:
    - Internal Research
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-08-14
tags:
    - attack.execution
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\aspnet_compiler.exe'
        TargetFilename|contains|all:
            - '\Temporary ASP.NET Files\'
            - '\assembly\tmp\'
            - '.dll'
    condition: selection
falsepositives:
    - Legitimate assembly compilation using a build provider
level: medium

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