AspNetCompiler Execution

Hunt Hypothesis

Detects execution of “aspnet_compiler.exe” which can be abused to compile and execute C# code.

Detection Rule

Sigma (Original)

title: AspNetCompiler Execution
id: a01b8329-5953-4f73-ae2d-aa01e1f35f00 # Exec
related:
    - id: 9ccba514-7cb6-4c5c-b377-700758f2f120 # SuspChild
      type: similar
    - id: 4c7f49ee-2638-43bb-b85b-ce676c30b260 # TMP File
      type: similar
    - id: 9f50fe98-fe5c-4a2d-86c7-fad7f63ed622 # Susp Paths
      type: similar
status: test
description: Detects execution of "aspnet_compiler.exe" which can be abused to compile and execute C# code.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Aspnet_Compiler/
    - https://ijustwannared.team/2020/08/01/the-curious-case-of-aspnet_compiler-exe/
author: frack113
date: 2021-11-24
modified: 2025-02-24
tags:
    - attack.execution
    - attack.stealth
    - attack.t1127
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|contains:
            - ':\Windows\Microsoft.NET\Framework\'
            - ':\Windows\Microsoft.NET\Framework64\'
            - ':\Windows\Microsoft.NET\FrameworkArm\'
            - ':\Windows\Microsoft.NET\FrameworkArm64\'
        Image|endswith: '\aspnet_compiler.exe'
    condition: selection
falsepositives:
    - Unknown
level: medium

KQL (Azure Sentinel)

imProcessCreate
| where (TargetProcessName contains ":\\Windows\\Microsoft.NET\\Framework\\" or TargetProcessName contains ":\\Windows\\Microsoft.NET\\Framework64\\" or TargetProcessName contains ":\\Windows\\Microsoft.NET\\FrameworkArm\\" or TargetProcessName contains ":\\Windows\\Microsoft.NET\\FrameworkArm64\\") and TargetProcessName endswith "\\aspnet_compiler.exe"

Required Data Sources

False Positive Guidance

• Unknown

MITRE ATT&CK Context

• Tactic: Execution
• Technique: T1127 — T1127

References

• https://lolbas-project.github.io/lolbas/Binaries/Aspnet_Compiler/
• https://ijustwannared.team/2020/08/01/the-curious-case-of-aspnet_compiler-exe/
• SigmaHQ Rule