Tool_MSIL_CSharpUtils_1
YARA-2025-0925
Medium
general
Active
The TypeLibGUID present in a .NET binary maps directly to the ProjectGuid found in the '.csproj' file of a .NET project. This rule looks for .NET PE files that contain the ProjectGuid found in the 'CSharpUtils' project.
Tool_MSIL_CSharpUtils_1.yar
Valid Syntax
// Copyright 2020 by FireEye, Inc.
// You may not use this file except in compliance with the license. The license should have been received with this file. You may obtain a copy of the license at:
// https://github.com/fireeye/red_team_tool_countermeasures/blob/master/LICENSE.txt
rule Tool_MSIL_CSharpUtils_1
{
meta:
description = "The TypeLibGUID present in a .NET binary maps directly to the ProjectGuid found in the '.csproj' file of a .NET project. This rule looks for .NET PE files that contain the ProjectGuid found in the 'CSharpUtils' project."
md5 = "dd8805d0e470e59b829d98397507d8c2"
rev = 1
author = "FireEye"
strings:
$typelibguid0 = "2130bcd9-7dd8-4565-8414-323ec533448d" ascii nocase wide
$typelibguid1 = "319228f0-2c55-4ce1-ae87-9e21d7db1e40" ascii nocase wide
$typelibguid2 = "4471fef9-84f5-4ddd-bc0c-31f2f3e0db9e" ascii nocase wide
$typelibguid3 = "5c3bf9db-1167-4ef7-b04c-1d90a094f5c3" ascii nocase wide
$typelibguid4 = "ea383a0f-81d5-4fa8-8c57-a950da17e031" ascii nocase wide
condition:
(uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550) and any of them
}Rule Metadata
description
The TypeLibGUID present in a .NET binary maps directly to the ProjectGuid found in the '.csproj' file of a .NET project. This rule looks for .NET PE files that contain the ProjectGuid found in the 'CSharpUtils' project.
md5
dd8805d0e470e59b829d98397507d8c2
author
FireEye
String Definitions
{"name":"$typelibguid0","value":"\"2130bcd9-7dd8-4565-8414-323ec533448d\" ascii nocase wide"}
{"name":"$typelibguid1","value":"\"319228f0-2c55-4ce1-ae87-9e21d7db1e40\" ascii nocase wide"}
{"name":"$typelibguid2","value":"\"4471fef9-84f5-4ddd-bc0c-31f2f3e0db9e\" ascii nocase wide"}
{"name":"$typelibguid3","value":"\"5c3bf9db-1167-4ef7-b04c-1d90a094f5c3\" ascii nocase wide"}
{"name":"$typelibguid4","value":"\"ea383a0f-81d5-4fa8-8c57-a950da17e031\" ascii nocase wide"}
Threat Analysis
This YARA rule is designed to detect general threats.
Severity Level: Medium
The rule uses pattern matching to identify specific byte sequences, strings, or behavioral patterns associated with malicious activity.
Detection Capabilities
- File-based detection for executables and documents
- Memory scanning for running processes
- Network traffic analysis support
Command Line Usage
# Scan a single file yara Tool_MSIL_CSharpUtils_1.yar /path/to/suspicious/file # Scan a directory recursively yara -r Tool_MSIL_CSharpUtils_1.yar /path/to/directory/ # Scan with metadata output yara -m Tool_MSIL_CSharpUtils_1.yar target_file # Scan process memory (Linux) yara Tool_MSIL_CSharpUtils_1.yar /proc/[pid]/exe
Integration Examples
Python (yara-python)
import yara
rules = yara.compile(filepath='Tool_MSIL_CSharpUtils_1.yar')
matches = rules.match('/path/to/file')
ClamAV Integration
clamscan --yara-rules=Tool_MSIL_CSharpUtils_1.yar /path/to/scan
Rule Information
YARA ID
YARA-2025-0925
Author
Repository
Created
August 19, 2025
Last Updated
August 19, 2025
Last Imported
Never
Threat Intelligence
Risk Level
Medium
Category
general
Detection Confidence
Analysis Pending
False Positive Rate
Not Available
Last Seen in Wild
No Data
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