Building Custom Malware Analysis Tools with Python

A guide to building custom tools for malware analysis, from basic parsers to advanced analysis frameworks.

Why Build Custom Tools?

While commercial and open-source tools exist, custom tools offer:

• Specific functionality for your use case
• Integration with your workflow
• Learning opportunities
• Flexibility and customization

Getting Started

Essential Libraries

import pefile      # PE file parsing
import capstone    # Disassembly
import yara        # Pattern matching
import hashlib     # Hashing

Basic PE Parser

import pefile

def analyze_pe(filepath):
    pe = pefile.PE(filepath)
    print(f"Architecture: {pe.FILE_HEADER.Machine}")
    print(f"Entry Point: {hex(pe.OPTIONAL_HEADER.AddressOfEntryPoint)}")
    
    # Analyze imports
    for entry in pe.DIRECTORY_ENTRY_IMPORT:
        print(f"Imports from: {entry.dll.decode()}")

Advanced Features

YARA Integration

import yara

rules = yara.compile('malware_rules.yar')
matches = rules.match('suspicious_file.exe')

Disassembly Analysis

from capstone import *

md = Cs(CS_ARCH_X86, CS_MODE_64)
for i in md.disasm(code, 0x1000):
    print(f"0x{i.address:x}:\t{i.mnemonic}\t{i.op_str}")

Building a Framework

Structure your tool as a modular framework:

• Parser modules
• Analysis engines
• Reporting modules
• Configuration management

Best Practices

• Error handling
• Logging
• Documentation
• Testing
• Performance optimization

Conclusion

Custom tools are powerful additions to any malware analyst's toolkit. Start simple and iterate based on your needs.