Reverse Engineering
Reverse Engineering
What is reverse engineering?
- Rebuilding the design from the finished product
- The goal is usually understanding, not copying
- AI agents have lowered the barrier
Normal development starts from a design and ends with a product. Reverse engineering flips that direction: it starts from a finished product you already hold and works backward to the design and principles behind it. For a machine, that means taking it apart and measuring the parts and dimensions. For software, it means observing what an executable, app, or web page actually does and reading its internal code. The goal is usually understanding, not copying. Remaking a discontinued part, migrating an old in-house system with lost documentation to a new one, and finding out what a piece of malware is stealing all fall under this.
Software reverse analysis falls into two approaches: static analysis, which reads the file itself without running the program, and dynamic analysis, which runs it and watches changes on screen, on the network, and in files. Static analysis uses a decompiler to turn machine code back into a human-readable form. Keep in mind that the result is not the original source but a reconstruction that estimates the original, because variable names, comments, and the developer’s intent are already lost during compilation.
For non-technical organizations, this concept comes up in more everyday situations than you might expect. Acceptance testing when you take delivery of outsourced software, to check it was built to the contract; security reviews to see whether personal data is leaking somewhere it shouldn't; and rebuilding the rules of a business system that only a departed employee understood are all forms of reverse engineering. The key is to decide what you want to know before you start. The narrower the question, as in 'Tell me how it calculates completed hours' rather than 'Analyze the whole program,' the faster and more accurate the result.
What changed in 2026 is that AI has joined the work. Tools like REA connect professional analysis tools such as Ghidra and IDA to an AI agent, so a trace that once took a security expert days can now start with a single plain-language question. That makes the boundaries all the more important. First check the target’s terms of service and what copyright law allows, and distinguish building something new from the principles you learned from copying someone else’s code. Understanding is reverse engineering; the moment you copy, it becomes a different matter.
Seolyeong ParkGenerative AI and AX training expert with 17 years of hands-on experience and 200+ sessions, making AI usable right away even for non-specialists
Seungtae ParkPractical AX instructor who teaches by building AI business development and marketing automation hands-onThe term comes from the practice in manufacturing and the military of taking apart an opponent's equipment to learn its design. In software, the standard definition comes from a 1990 IEEE Software paper by Elliot Chikofsky and James Cross, who defined it as 'the process of analyzing a subject system to identify its components and their relationships and to create representations of the system at a higher level of abstraction.'
Here is a hypothetical case. Company A, a machine parts manufacturer with 610 employees, had used a training records program built by an outside vendor in 2011 for 15 years. They decided to move to a new LMS, but the vendor had gone out of business and neither the source code nor the design documents existed anywhere.
- Jung, a manager on the talent development team, asked around about the rules behind how an old program processed statutory mandatory training completions. The only person who knew was a predecessor who had already left the company.
- Before starting, Oh, an assistant manager on the information security team, confirmed with the legal team that the company had paid for the program and owned it as an in-house asset, and checked the rights clauses in the contract.
- When Oh, an assistant manager, connected an analysis tool to an AI coding agent and had it examine the executable, a hidden rule surfaced within two days: completed hours were rounded up in 30-minute increments, not counted by the minute.
- Using the same approach, they documented 14 rules, including completion criteria and retake handling. Three differed from current company policy, and HR corrected them before moving to the new LMS.
- In the first quarter after the migration, not a single employee’s training-hour totals differed from the old system’s, and the KRW 24 million (≈ US$18,000) re-analysis the outside vendor had quoted never became necessary.