Forward & Reverse Engineering

How frequently do you hear the term “reverse engineering” in the cyber world? Often, right! To understand reverse engineering properly, we must first grasp what engineering itself is. Let’s explore both forward and reverse engineering concepts — after all, if you want to reverse a car, you need to first learn how to drive forward!

Engineering is the application of scientific and mathematical principles to design, build, and optimize structures, systems, and technologies that solve real-world problems.

Forward Engineering

In software engineering:

• Conceptualization: We begin by defining what we want to create — the problem we’re solving.
• Implementation: We write code in a programming language that expresses our solution.
• Compilation: This code transforms through compilation (sometimes including Just-In-Time compilation) into machine-readable instructions.
• Execution: Finally, the program runs, performing the intended functions.

What’s fascinating is that information is lost at each step of this process. The original intent, the elegant design patterns, the carefully chosen variable names — all gradually fade away as we move toward executable code.

Reverse Engineering: Working Backwards

Reverse engineering is the process of analyzing a system, product, or software to understand its design, functionality, or structure, often to recreate, improve, or identify vulnerabilities.

Reverse engineering works in the opposite direction. Starting with only the finished product, engineers attempt to understand:

• What does this software do?
• How does it accomplish its tasks?
• What algorithms and data structures does it use?
• How can we interact with or modify it?

Reverse Engineering Process

1. Binary Analysis: Starting with compiled code (binary executables), we examine the machine instructions.

• File Format Analysis: Understanding the structure of EXE, DLL, ELF, or other executable formats
• Initial Reconnaissance: Identifying basic information like target architecture, compiler used, and linked libraries
• String Extraction: Finding text strings that might reveal functionality or error messages

2. Disassembly: Converting machine code back into assembly language for human readability.

• Disassemblers like IDA Pro, Ghidra, or Radare2 convert binary opcodes into assembly instructions
• Engineers identify key program components like functions, loops, and conditional branches
• This provides a low-level view of program execution

3. Decompilation: Attempting to recreate higher-level code from assembly.

• Modern decompilers like Ghidra’s decompiler or Hex-Rays can generate C-like pseudocode
• This makes the code much more readable and easier to understand
• The resulting code won’t be identical to the original but captures the functionality

4. Behavior Analysis: Observing how the program runs, interacts with the system, and handles inputs.

• Network communications and protocols
• File system operations
• Registry or configuration changes
• User interface elements and workflows

5. Documentation: Recording discoveries about program structure, algorithms, and functionality.

Why Information Recovery is Challenging

Remember the information loss we mentioned in forward engineering? This is where it becomes most apparent:

• Variable names are replaced with generic identifiers or memory addresses
• Comments explaining developer intentions are completely removed
• High-level structures like classes and functions may be optimized and transformed
• Compiler optimizations may reorganize code in ways that obscure the original logic.

Ethical and Legal Considerations

• Copyright Law — Some products, especially software, are protected by copyright, which can make reverse engineering legally questionable in certain cases.
• DMCA (Digital Millennium Copyright Act) — This law in the U.S. mostly restricts reverse engineering but allows exceptions for security research, encryption testing, and interoperability.
• EULAs (End-User License Agreements) — Many software agreements explicitly prohibit reverse engineering, meaning breaking these terms could lead to legal trouble.
• Legitimate Uses — Many countries allow reverse engineering for specific reasons, such as making different software work together (interoperability), improving security, or for educational purposes.

This is just the beginning — a brief introduction. In the next part, we’ll get into reverse engineering of malware and the fundamentals of malware analysis. Keeping blogs concise due to time constraints, but ensuring every reader finds the content valuable and worth their time.