Shellcode Analysis Tools

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).