Hex Editor vs. Binary Viewer: Which Tool Do You Need?

Advanced Hex Editing: Techniques for Reverse Engineering

Overview

Advanced hex editing is using a hex editor plus static/dynamic analysis to inspect, modify, and patch binaries at the byte level. It’s a practical skill in reverse engineering for unpacking/probing file formats, changing control flow, removing checks, and recovering data.

Key techniques

• Identify file type and important offsets

  • Locate file signatures (magic bytes) and header fields (e.g., PE MZ/PE header, ELF e_ident).
  • Use structure viewers (ImHex, 010 Editor templates) to map fields to offsets.

• String and pattern discovery

  • Extract ASCII/UTF-16 strings to find messages, format specifiers, and function names.
  • Search for known byte patterns (opcodes, imports, signatures) to locate routines.

• Cross-reference with disassembler/decompiler

  • Open the binary in IDA/Ghidra/Radare2 to identify functions/OEP; use hex editor for final byte-level patches.
  • Use decompiler output to find exact bytes to modify for logic changes.

• Patching code and data

  • Overwrite instructions with NOPs or short jumps to skip checks.
  • Replace conditional branches by flipping opcode bytes or changing immediate operands.
  • Update checksums, sizes, and table entries after edits (PE checksum, length fields).

• Binary patching workflow

  1. Make a backup and work on copies.
  2. Confirm target architecture/endianness.
  3. Locate target bytes (disassembler + pattern search).
  4. Test small edits in an emulator or sandboxed VM.
  5. Fix collateral fields (relocations, checksums) and retest.

• Working with executables (PE/ELF/Mach-O)

  • For PE: Edit Import/Export tables, entry point, and sections; use CFF Explorer or rizin to rebuild headers.
  • For ELF: Watch program headers, dynamic symbols, and relocations; adjust section offsets if changing sizes.
  • Preserve alignment and section boundaries or rebuild with tools after structural edits.

• Repairing and rebuilding after memory dumps

  • Use ImHex/Scylla/CFF Explorer to detect MZ/OEP and reconstruct import tables.
  • Compare multiple dumps (different load addresses) to recover relocation info.

• Using templates, signatures, and interpreters

  • Use ImHex or 010 Editor templates to parse common structures quickly.
  • Apply FLIRT signatures (IDA) or known pattern databases to identify library code.

• Automation & scripting

  • Script repetitive edits with IDA Python, rizin/radare2 scripts, or editor macros.
  • Use checksumming and binary-diff scripts to validate changes.

Tools commonly used

• Hex editors: ImHex, HxD, 010 Editor, Hex Workshop
• Disassemblers/decompilers: IDA Pro, Ghidra, Hopper
• Debuggers/runtime tools: x64dbg, WinDbg, lldb, Frida, Scylla
• PE/ELF helpers: CFF Explorer, rizin/radare2, pe-sieve, lief

Safety and best practices

• Work on copies; use VMs/sandboxes for testing.
• Track every byte change (diffs) and restore points.
• Recompute checksums and verify imports/relocations after edits.
• Test on multiple inputs and in a controlled environment.

Quick example (conceptual)

• Goal: bypass a license check that compares a value and returns early.
  1. Locate the compare+conditional-jump in the disassembler.
  2. Note the jump opcode bytes and offset.
  3. In hex editor, replace the conditional jump with NOPs or an unconditional jump to continue execution.
  4. Recompute any affected checksums and test in sandbox.

If you want, I can produce a step-by-step walkthrough for a specific binary format (PE/ELF) or show exact byte edits for a short sample executable.