Agent skill

analyzing-dotnet-assemblies

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Forks 31

Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/analyzing-dotnet-assemblies

SKILL.md


name: analyzing-dotnet-assemblies description: >- Analyze .NET assemblies to decompile IL code, inspect metadata, extract embedded resources, and identify malicious functionality. domain: cybersecurity subdomain: reverse-engineering tags:

  • dotnet
  • csharp
  • il-code
  • dnspy
  • decompilation version: "1.0" author: defconxt license: AGPL-3.0 metadata: mitre-attack: ["T1027", "T1059.001"] cwe: ["CWE-506"] tools: ["dnSpy", "ILSpy", "de4dot", "monodis", "dotPeek"]

Analyzing Dotnet Assemblies

Overview

Analyze .NET assemblies to decompile IL code, inspect metadata, extract embedded resources, and identify malicious functionality.

Prerequisites

Tool / Requirement Details
dnSpy Security tooling
ILSpy Security tooling
de4dot Security tooling
monodis Security tooling
dotPeek Security tooling
Isolated lab environment for testing Environment requirement
Authorization and signed Rules of Engagement (RoE) Environment requirement
Relevant target samples or systems acquired through authorized channels Environment requirement

Quick Reference

bash
# Decompile with ILSpy CLI
ilspycmd ./target.dll -o ./decompiled/

# Inspect assembly metadata
monodis --typedef ./target.dll
monodis --method ./target.dll

# Deobfuscate .NET
de4dot ./target.exe -o ./cleaned.exe

# Extract embedded resources
python3 -c "
import dnfile
pe = dnfile.dnPE('./target.dll')
for r in pe.net.resources:
    print(f'{r.name}: {r.size} bytes')
"

Workflow

Step 1: Preparation and Reconnaissance

bash
# Identify target and gather initial intelligence
file ./target_sample
dnspy --version 2>/dev/null || echo "Install dnSpy"

# Set up working directory
mkdir -p /tmp/analyzing-dotnet-assemblies/{output,logs,artifacts}

Step 2: Primary Analysis

bash
# Execute primary analysis with dnSpy
# Refer to Quick Reference above for detailed commands
echo "[*] Running Analyzing Dotnet Assemblies with dnSpy..."

# Log all operations
script -q /tmp/analyzing-dotnet-assemblies/logs/session.log

Step 3: Deep Investigation

bash
# Apply ILSpy for secondary analysis
echo "[*] Deep investigation with ILSpy..."

# Cross-reference findings
diff /tmp/analyzing-dotnet-assemblies/output/primary.json /tmp/analyzing-dotnet-assemblies/output/secondary.json

Step 4: Documentation and Reporting

bash
# Generate structured findings report
cat <<'EOF' > /tmp/analyzing-dotnet-assemblies/output/report.json
{
  "technique": "analyzing-dotnet-assemblies",
  "domain": "reverse-engineering",
  "tools_used": ["dnSpy", "ILSpy"],
  "findings": [],
  "recommendations": []
}
EOF

Detection

yaml
title: Dotnet Assemblies Detection
id: df17ae97-986d-41f9-96af-ac65538ebd02
status: experimental
description: Detects suspicious activity related to analyzing dotnet assemblies techniques in reverse engineering context
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine: "*analyzing*dotnet*"
  condition: selection
level: medium
tags:
  - attack.t1027
  - attack.t1059.001
  - attack.defense_evasion
falsepositives:
  - Malware analysis sandbox performing automated binary inspection

Detection Opportunities

Indicator Source Detection Logic
Dotnet Assemblies Detection windows/process_creation Sigma rule (medium)
ATT&CK Coverage MITRE ATT&CK T1027, T1059.001

Verification

  • Environment and tools verified and operational
  • Target samples acquired through authorized channels
  • Primary analysis completed with findings documented
  • Secondary validation performed with independent tooling
  • All artifacts preserved in structured output directory
  • Detection opportunities documented for blue team

References

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