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.NET Malware 101

.NET Malware 101

The .NET framework gives malware authors the same things it gives legitimate developers: fast development, a rich class library, and tight Windows integration. Ransomware, credential stealers, wipers, and remote access trojans are all routinely written in .NET, which makes reading compiled .NET assemblies a practical skill for anyone triaging Windows threats.

This section covers what a .NET binary actually contains and how to navigate it with tools like dnSpy, ILSpy, and PEStudio.

  • Analyzing the .NET Executable File Structure - How managed code is compiled and executed by the CLR, what lives inside a .NET assembly, and a guided tour of the CLR runtime header, metadata streams, metadata tables, tokens, the manifest, and method body headers, using the Sunburst (SolarWinds) sample as the worked example.