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Shellcode Analysis Tools

G5 Cyber Security

TL;DR

Analysing shellcode – small pieces of code used in cyber security attacks – requires specific tools. This guide covers several options, from debuggers to online analysis services and disassemblers, suitable for different skill levels.

Shellcode Analysis Tools: A Practical Guide

  1. Understand What You’re Dealing With
    • Shellcode is often platform-specific (Windows, Linux, etc.). Knowing the target architecture (x86, x64, ARM) is crucial.
    • It’s usually raw machine code, so you need tools that can interpret it.
  2. Debuggers
    • GDB (GNU Debugger): Powerful for Linux shellcode analysis. 
      gdb -q ./shellcode_file

      Then use commands like disassemble, break *address, and stepi to examine the code.

    • x64dbg/OllyDbg: Excellent for Windows shellcode.
      1. Load the shellcode into the debugger (often by creating a small executable that calls it).
      2. Use breakpoints and single-stepping to follow execution.
      3. Pay attention to API calls – these reveal what the shellcode is trying to do.
  3. Disassemblers
    • IDA Pro: Industry standard, but commercial (expensive). Provides very detailed disassembly and analysis features.
    • Radare2: Free and open-source. A powerful command-line disassembler and debugger. 
      r2 -q ./shellcode_file

      Use pd @ address to disassemble at a specific address, or izz for the full disassembly.

    • Binary Ninja: Commercial but with a free personal license. Offers a good balance of features and usability.
  4. Online Analysis Services
    • Hybrid Analysis: Upload shellcode to get reports on its behaviour, including API calls, strings, and potential malicious activity. https://www.hybrid-analysis.com
    • VirusTotal: While primarily a malware scanner, it can provide some basic shellcode analysis information (strings, imports). https://www.virustotal.com
  5. Shellcode Emulators/Decompilers
    • Capstone: A lightweight disassembly framework that can be integrated into your own tools or scripts. 
      # Example in Python (requires Capstone installation)
import capstone
md = capstone.Cs(capstone.CS_ARCH_X86, capstone.CS_MODE_32)
for i in md.disasm('your shellcode here', 0x1000):
  print(i)
    • Unicorn Engine: A CPU emulator that allows you to execute shellcode in a controlled environment.
  6. Static Analysis Techniques
    • String Extraction: Use tools like strings (Linux/macOS) or a hex editor to identify embedded strings. This can give clues about the shellcode’s purpose. 
      strings ./shellcode_file
    • API Call Identification: Look for patterns that indicate specific API calls (e.g., CreateFileA, LoadLibraryA on Windows).
  7. Dynamic Analysis Techniques
    • Run the shellcode in a controlled environment (VM) and monitor its behaviour using tools like Process Monitor (Windows) or strace (Linux).
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