Researchers Weaponize and Obfuscate .NET Assemblies Using MacroPack

Researchers at BallisKit have introduced a sophisticated scenario within their MacroPack Pro tool to obfuscate and weaponize .NET assemblies, significantly enhancing their stealth against modern security solutions.

As .NET has become a preferred language for crafting prominent offensive tools like Rubeus, SeatBelt, SharpDPAPI, and Certify over recent years, its widespread use has also drawn the attention of defensive mechanisms.

The intermediate language (IL) in .NET binaries retains most source code symbols even in release mode, making it easier for security products to develop detection signatures.

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Addressing this challenge, BallisKit’s latest innovation offers a robust framework to obscure these assemblies, rendering them less detectable while maintaining their malicious functionality.

Innovative Techniques to Evade Detection

The MacroPack Pro tool integrates a private .NET obfuscator through its WEAPONIZE_DOTNET template, providing multiple obfuscation options to transform assemblies into stealthier versions.

One key feature, the obfuscate-dotnet-dinvoke-mutation option, converts static PInvoke imports used for calling native functions with cleartext library and function names into dynamic DInvoke imports.

According to BallisKit reports, this shift obscures the imported functions at runtime, reducing the visibility of malicious intent to static analysis by security tools, though it introduces potential detection risks via delegate usage.

Another critical option, obfuscate-dotnet-reflection-handling, manages .NET’s reflection capabilities, ensuring that obfuscated symbols are mapped back to their original values during runtime to prevent functionality breaks, albeit with a slight increase in assembly size and execution time.

Additionally, options like obfuscate-dotnet-embed embed the obfuscated assembly within a .NET loader to avoid disk writes, while obfuscate-dotnet-inflate reduces entropy at the cost of a larger file size, further evading static analysis.

Deployment Strategies

Beyond obfuscation, MacroPack Pro facilitates weaponization by enabling deployment through various formats tailored for red team operations.

Assemblies can be packaged as standalone executables for direct execution on target systems or embedded into scripting languages such as Visual Basic Script (VBS), JavaScript, HTA documents, or Batch scripts, preserving command-line argument functionality.

For environments with stringent security, the tool supports integration into Office documents via VBA macros, using environment variables like CONSOLE_ARGUMENTS and CONSOLE_OUTPUT to handle input and output since Office applications detach from console interfaces.

Compatibility is maintained with .NET Framework versions as far back as 3.5, aligning with Windows 7’s default runtime, though the original assembly’s target framework dictates broader compatibility.

Extensive testing by BallisKit confirms the efficacy of these techniques, with obfuscated assemblies like KrbRelay, Rubeus, Mythic Apollo Implant, SeatBelt, SharpDPAPI, and SharpHound retaining full functionality while bypassing many security solutions.

This development underscores a significant advancement in offensive tooling, challenging defenders to adapt to increasingly sophisticated evasion tactics.

As .NET remains a cornerstone of malicious tooling, the innovations in MacroPack Pro highlight the ongoing cat-and-mouse game in cybersecurity, pushing the boundaries of both attack and defense strategies in the digital landscape.

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