Add DecompressEXE signature for memory analysis

[kevross33]

This module defines a signature for detecting decompression of executables in memory, which may indicate the use of packers or manual loaders.

Pikabot:

[gemini-code-assist]

Summary of Changes

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This pull request enhances the malware analysis capabilities by introducing a new signature designed to identify executables that decompress themselves in memory. This is a crucial step in detecting packed or manually loaded malware, providing deeper insight into their runtime behavior and improving the overall efficacy of threat detection.

Highlights

• New Cuckoo Signature: A new Cuckoo Sandbox signature, DecompressEXE, has been added to detect in-memory decompression of executables.
• Detection Logic: The signature specifically monitors for calls to the RtlDecompressBuffer API and checks if the resulting uncompressed buffer begins with the 'MZ' magic bytes, indicating a Portable Executable (PE) file.
• Malware Analysis Focus: This detection aims to identify the use of packers or manual loaders, which are common techniques used by malicious software to evade detection and obfuscate their true nature.

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Changelog

• modules/signatures/windows/packer_decompress_buffer.py
  • Added a new file defining the DecompressEXE signature.
  • Implemented logic to detect RtlDecompressBuffer API calls.
  • Included a check for the 'MZ' header in the uncompressed buffer to confirm it's an executable.
  • Configured signature metadata including severity, confidence, categories (packer), authors, minimum Cuckoo version, and relevant MITRE ATT&CK (TTPs) and Malware Behavior Catalog (MBCs) identifiers.

Activity

• No human activity has occurred on this pull request yet.

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Code Review

This pull request introduces a new Cuckoo signature to detect in-memory decompression of executables by monitoring RtlDecompressBuffer API calls. The overall logic is sound, but I've identified a critical issue that could lead to a crash, as well as several opportunities for simplification and adherence to the framework's patterns. Additionally, some of the MITRE ATT&CK and MBC references appear to be invalid.