C# IL Code Compilation Via Ilasm.EXE — Sigma Rule

Rule metadata and linked tags

Author: frack113, Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-05-07 / 2022-05-16.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 34e7ef61d405f0d343ce3e5c1ec89293b1f4f9709252b563aff5a2aad49a7016

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: C# IL Code Compilation Via Ilasm.EXE
id: 850d55f9-6eeb-4492-ad69-a72338f65ba4
status: test
description: Detects the use of "Ilasm.EXE" in order to compile C# intermediate (IL) code to EXE or DLL.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Ilasm/
    - https://www.echotrail.io/insights/search/ilasm.exe
author: frack113, Nasreddine Bencherchali (Nextron Systems)
date: 2022-05-07
modified: 2022-05-16
tags:
    - attack.execution
    - attack.stealth
    - attack.t1127
logsource:
    product: windows
    category: process_creation
detection:
    selection_img:
        - Image|endswith: '\ilasm.exe'
        - OriginalFileName: 'ilasm.exe'
    selection_cli:
        CommandLine|contains:
            - ' /dll'
            - ' /exe'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://lolbas-project.github.io/lolbas/Binaries/Ilasm/
• https://www.echotrail.io/insights/search/ilasm.exe