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Analysis: Reverse Engineering and You
Analysis: Reverse Engineering and You Exclusive
January 22, 2010 | By Mona Ibrahim

January 22, 2010 | By Mona Ibrahim
More: Console/PC, Exclusive

[What are the legal implications of reverse engineering games? Attorney Mona Ibrahim looks at the issue for Gamasutra, from consumer protections to EULA-based restrictions.]

Let's begin with a story.

Mallory the Mythical Developer and two of her good buddies are fans of Katarina's Conquest, a FPS loosely based on the Bolshevik Revolution of 1917. The game incorporates modern weaponry in a historical, beautiful, and immersive environment.

October Industries, the developers of the game, had no idea it would be such a great success upon release. Its servers are, unfortunately, completely unable to handle the huge number of new users, and the game hasn't stayed up for more than thre consecutive hours since launch.

So Mallory and her friends decide to host a private server where they can play the game with a handful of their other friends across the globe. This means no more worrying about the server shutting down. To do this, they will have to use reverse engineering to translate the game's network protocol so their game clients can communicate with the new server.

Mallory, being an experienced and business-savvy developer, immediately recognizes that there may be some legal problems here.

And Mallory is right: Reverse engineering can be a risky endeavor and shouldn't be attempted without first consulting an attorney. Below, I'll discuss what reverse engineering is, how it's accomplished, and, more importantly, when reverse engineering will put you and your development team at risk.

What is Reverse Engineering?

Reverse engineering of computer software is any method of studying a program for the purpose of obtaining useful and detailed information about the functional components and mechanisms of the program in question. The Supreme Court defines it as a “fair and honest means... [of] starting with the known product and working backward to divine the process which aided in its development or manufacture."

This can be as simple as observing gameplay to determine the functional elements of the game's rule set or as complex as decompiling a file and analyzing its components to learn how ads are displayed across the game server.

Tools used to reverse engineer a game include debuggers, disassemblers, and network protocol analyzers (packet sniffers). The essential function of these tools is to give the programmer access to data revealing the precise functions and mechanics of a program so those functions and mechanics can be reproduced with minimal or no use of the original source or binary code.

This method of learning functions and processes has historically been viewed as fair game by most developers. Indeed, to some extent it is still protected under the legal doctrine of “fair use.” As a result, inventors in the field of technology and software have relied on reverse engineering for decades.

For example, while the Copyright Act protects the three-dimensional patterns and designs of a microchip, it expressly allows the reverse engineering of those patterns and designs (referred to by the Act as a “mask work”) to analyze the concepts or techniques embodied in the chip. Using similar logic, courts have found that analyzing a computer program for the sole purpose of learning and reproducing its precise functions (provided those functions are not otherwise protected under patent law) is typically fair use.

This does not, however, mean that all reverse engineering is treated equally under the law. In software development, the practice of reverse engineering has come under assault over the past several years.

Copyright and the DMCA Anti-Circumvention Act

Machine code and source code are protected as literary works under the Copyright Act. The copying of software code without permission is copyright infringement. Using any part of someone else's unique code in your own project, particularly non-functional code, without permission can give rise to an infringement claim.

Sometimes during the process of reverse engineering, the programmer may want to copy a data file or the entire program. Typically that type of copying is not permitted under the Copyright Act, although there are a few, very limited, exceptions. For example, backup files are allowed for a legal purpose such as repairing or debugging a lawfully-owned program.

Yet the Copyright Act's protection of computer software goes well beyond the question of whether you've copied anything. In fact, you don't need to copy any code at all to run afoul of U.S. copyright law. The anti-circumvention provision of the DMCA, 17 U.S.C. 1201, prohibits the circumvention of any technological measures that control access to any part of the work. It also prevents the distribution of software that enables circumvention of an access control.

Circumvention under the Act means descrambling or decrypting a work, or otherwise bypassing, removing, deactivating or impairing any technological measure without permission.

There are a few classic examples of such technological measures: Remember those old Sierra games that required you to input a word from a specific paragraph on a specific page of the user manual before you could play the game? That's an access control. Data file encryption is a more specific application of an access control. CD key and license key encryption are other commonly-used methods.

Circumventing any of these methods to access the content is probably illegal under the DMCA -- but that isn't the only scenario where a programmer could find him or herself in hot water.

This is relevant to Mallory the Developer's case too. If Mallory's new server doesn't provide the same safeguards that control access to the original game servers (like a CD key or a version verification protocol), then her own server is circumventing access controls to the online component of the game. Therefore, by distributing the program, means (such as DIY instructions), or code to access servers that don't use the game's original access controls, she would be violating the anti-circumvention provision.

According to at least one court decision, this is sufficient to constitute a breach of 17 U.S.C. 1201 and thereby give rise to a statutory damages claim in the range of $2,500 to $25,000.

This does not mean that all aspects of reverse engineering are prohibited under the DMCA. For instance, analyzing unencrypted machine code in order to translate those processes and functions to source code is generally permissible. But because the statutory definition of “circumvention” is so broad under the act, you should be mindful of any encrypted or otherwise protected data contained in a program file if you attempt to lawfully reverse engineer a process or function.

There is one major exception to the DMCA: Bypassing or decrypting encrypted data files of a legally owned copy of a program for the sole purpose of making that program interoperable with other legal software (for instance, a different operating system) is expressly permitted under the DMCA.

However, this right is personal. You can't distribute a way to bypass a CD key or other cracking or decrypting software to make that software playable. This is why most interoperability projects, such as the adventure game virtual machine ScummVM, require end users to legally own the games they make playable. They cannot legally provide a means of playing cracked games, even if the primary purpose of the project is interoperability. This is key: interoperability must be the only purpose.

It is important to note here that this exception can be waived if you agree to a license that prohibits reverse engineering.

Contractual Safeguards

A less confusing but no less treacherous risk comes from contracts -- EULAs, NDAs, and other agreements -- that a programmer might subject him or herself to when licensing software. For years, courts have upheld contract provisions that limit the end user's right to reverse engineer a program for any purpose. Any form of agreement to a contract will suffice: click-wrap and shrink-wrap agreements are generally considered enforceable.

For example, if Katarina's Conquest includes an EULA that expressly prohibits reverse engineering, and Mallory clicked the “I Accept” button when installing the program, then Mallory should probably abandon hopes of creating a private server by reverse engineering the client. A programmer can be liable for breach of contract and other causes of action for violating a EULA, including misappropriation of trade secrets, in addition to the possible copyright claims..

Pay close attention to the EULA of any game or program you want to reverse engineer. Even if you hope to reverse engineer the program for legal purposes, you would still be prohibited if you've accepted the EULA's terms in any manner. This includes purchasing a product with a shrink wrap license or clicking the “I Accept” button during the installation process.

Privacy Rights

A final consideration to bear in mind is data privacy. In most situations involving reverse engineering of a game, developers like Mallory and her friends would only want to monitor her client's network communications with the game server. However, if you're working on the kind of project where you inspect network packets that aren't yours, then you should be aware of certain privacy laws.

The first is the Electronic Communications Privacy Act (ECPA), part of the Wiretap Act, (18 U.S.C. 2510 et. Seq.). Under the ECPA you can't intercept electronic communications, including data packets or any transfer of information between a client and a network provider, while that data is en route on a network unless you are the network provider (or a duly authorized government official authorized to access that information for investigative purposes). Violation of the ECPA could subject you to both civil and criminal liability.

The second law is the Stored Communications Act (18 U.S.C. 2701 et. Seq. ). This act is designed to prevent unauthorized access to network service providers that allow the transfer of private electronic communications. You can be criminally liable for accessing data temporarily stored at those points without authorization. You can also be liable for exceeding your authorization and obtaining data to which you shouldn't have access unless that access is expressly permitted under the statute.

Both of these laws are designed to prevent you from accessing private communications, including data packets sent over a network or temporarily stored on a network. For this reason alone, you should avoid reverse engineering projects that require monitoring communications you don't have permission to observe.


Reverse engineering isn't inherently illegal. As we've seen, though, it can involve a variety of legal issues. If Mallory and her friends move forward with their private server project they will need to determine their risk exposure and take steps to ensure that all aspects of the reverse engineering process is legally compliant. This isn't the type of project you want to pursue if you're risk averse; after all, reverse engineering is traditionally done for the purpose of recreating the useful functions of someone else's work. That alone can be enough to draw unwanted attention from content owners.

If you still want to engage in a reverse-engineering project, you can mitigate your risk by contacting an attorney to learn steps you should take to protect yourself and your project.

[Mona Ibrahim is a trademark, entertainment, and media law attorney based in Seattle, WA. She is Of Counsel with Imua Legal Advisors and her practice emphasizes copyright and trademark dispute resolution, IP registration, entertainment and media transactions, general business transactions, and employment law. Mona is an avid gamer and is dedicated to serving the gaming and game development communities by providing education, helpful strategy, and legal assistance when necessary.

THE INFORMATION IN THIS ARTICLE IS FOR EDUCATIONAL PURPOSES ONLY. The content of this article is not legal advice. It only constitutes commentary on legal issues, and is for educational and informational purposes only. Reading this article, replying to it via comments, or otherwise interacting with this article does not create an attorney-client privilege between you and the author. No information you provide in the comments portion of this article shall be deemed confidential.]

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Robert Lou
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This is a slight OT, but at first I thought someone actually made an FPS based on the Bolshevik rebellion. You had no idea how excited I was for a moment, and how let down I was after googling it and getting the gamasutra article as my first hit :P

Mike Lopez
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Hmmm. Good to know I guess. Call me a cynic but wouldn't the author's clients be all the big Publishers who own content and would therefore have a vested interest in dissuading (scaring) the public away from reverse engineering any of their works? I have no interest in reverse engineering, nor do I have the know-how to do so but I do wonder if all the motives here are not also serving double duty for those big fish publisher clients.

The irony of an article about the legality of reverse-engineering software is that more than one of the big game publishers of today were openly reverse engineering many of the early consoles (Genesis, SNES, PSOne, etc.) during the early and mid 90s as a matter of business in order to gain an early competitive edge, and also so they did not have to rely on notoriously weak development libraries at the time of launch or to compete for a limited amount of grossly over-priced dev systems. Now those publishers are the most vocal in crying foul when individuals do the same. I have no problem with enforcing against outright piracy but going after the Mallory's of the world seems pointless though I am sure it happens all too frequently.

Mona Ibrahim
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No, I do not represent any big publishers. On the contrary most of my game-industry work is education-oriented, and the clients I have in this sector are all small indie developers.

I don't know if what you're referring to is necessarily ironic. As I said, reverse engineering isn't inherently illegal; it's just not something you should pursue with your eyes shut to potential legal pitfalls. Several cases have dismissed reverse engineering charges (particularly in the console department) on the grounds that it is, in many cases, both legal and advantageous to public policy.

Chris Remo
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Not to put words in Mona's mouth, but this article doesn't espouse any moral judgments, only legal analysis. There's nothing ironic about what you describe. Regardless of whether the actions taken by such publishers were justifiable, there are legal considerations to consider in this area, and this article outlines many of them.

Tim Carter
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Mike, if you strike down IP rights because you don't like big publishers, you will strike down those rights for all of us.

Dan Rosenthal
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Hi Mona,

Great to see another article from you. One additional side note that I think might be relevant in your article: in addition to the provisions of section 1201 of the DMCA, it's potentially possible to run afoul of section 1202, which safeguards the integrity of copyright management information. For instance, lets say someone was reverse engineering a game, and some portion of the code was affixed with CMI (and by this, I mean in commented into the code). If that is modified or deleted in the reverse-engineering process it creates a situation where a violation of 1202(b) is possible, especially with the reduced scienter requirements (i.e. reasonable grounds to know that it would facilitate or enable an act of infringement).

It's especially relevant given the broad definition of CMI outlined in 1202(c): CMI can include simply the name of and identifying information of the work's author.

I just envision a situation where some aspiring reverse-engineer is pulling apart lines of code, and chops out the //commented lines identifying that particular bit of code's author and such (personal or corporate), and then when he gets hit with the the copyright infringement claim under the Copyright Act, and the 1201 claim under the DMCA, they also are able to slap on a 1202(b) claim because actions removed or modified CMI and he had reasonable grounds to know that doing so would facilitate the act of infringement.

Since 1202 claims are significantly more valuable in terms of statutory damages than 1201 claims, especially when you're looking at multiple violations or facing the treble damages clause, that could be a really bad situation.

Aesir Rising
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@Dan Rosenthal re: "..pulling apart lines of code, and chops out the // commented lines..."

Code comments exist in source code files. If you have source code, you're not reverse engineering anything. Unless I'm misunderstanding the scenario you envision.

Mike Lopez
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I stand corrected. My apologies.

Ron Newcomb
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Even in academia, Computer Science grad students, when they pick their specialization, are frequently steered away from studying reverse engineering. It's partly the universities' worry about liability should the student actually, you know, find magical ways of decompiling Microsoft Windows or whatnot, and partly that the job openings for such a specialty are rare. Many academic disciplines in the science & engineering side of things have their taboo specialties and black arts; decompilation is Computer Science's.

Roberto Alfonso
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Interesting article, and comments from Dan. I believe it is also legal to reverse engineer if the application holds a complete monopoly of the market and the company barred third parties from utilising its services. Don't take my word for it, but the few times I have been involved in reverse engineering our bosses told us it was perfectly legal because the application held a monopoly on its own and federal laws prevented them from that.

Unless our bosses lied ^_^;

Dan Rosenthal
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@Aesir Rising: The two aren't incompatible; for instance if one was able to gain access to a portion of the source code, but was forced to reverse-engineer the best. Or, (and here's where my coding knowledge fails as I'm a writer, not coder) aren't there decompilers out there that will literally revert a compiled, packaged game into its relevant source code files? Mona alludes to this in her article:

"Tools used to reverse engineer a game include debuggers, disassemblers, and network protocol analyzers (packet sniffers). The essential function of these tools is to give the programmer access to data revealing the precise functions and mechanics of a program so those functions and mechanics can be reproduced [...]"

Mona's comment also seems to allude to this qualifying as reverse-engineering.

"[...]with minimal or no use of the original source or binary code."

i.e. minimal is a non-zero value for use of the code.

I wouldn't want to speak for her as to whether she'd agree with my assessment, but I think it stands to reason that a plausible argument can be made. And of course the 1202 removal/modification of CMI claim can stand so long as it was enabling or facilitating the act of infringement; it does not have to happen at the same time. There is a lot of room for creative arguing by plaintiff's attorneys here to paint a reverse-engineer in a negative light, as Mona points out with the large number of potential causes of action they can play with.

Wyatt Epp
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It's a bit more complicated than that, actually. The first thing to know is that comments in code are so-called because they are ignored by the compiler; they're not part of the binary. This is why one can put a line or block of code in comments and it won't end up in the compiled binary. This doesn't preclude files that are interpreted from bare ASCII, but from what I've seen, that's rather rare in a shipping product.

Second, disassembly doesn't return things to the state of the original source; this is actually nigh-impossible, even with substantial human input (assuming a release build. Why would your users have a debug build anyway?). It puts it in an intermediate (processor-specific) state that's just one step removed from machine code, where much of what you see is direct manipulation of individual numbers and addresses. For a more striking comparison, consider the following:

C Code:

int main() {

write(1,"Hello World!n", 13);

return 0;


objdump Disassembly:

push %rbp

mov %rsp,%rbp

mov $0xd,%edx

mov $0x400624,%esi

mov $0x1,%edi

mov $0x0,%eax

callq 400440

mov $0x0,%eax



Quite the difference, eh? And that's about as simple as a program can get; even a tiny game is several orders of magnitude more complex.

You may note the presence of the write call in the assembly, but it's rather common for commercial developers to take steps to obfuscate the names of program symbols, so it can be extremely difficult to make heads or tails of these things.

And there you have it: a brief and incomplete intro to that gray area down near the metal! Hope this is understandable.

Dan Rosenthal
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It is, thanks. Still, I think the risk exists potentially somewhere in any of the thousands of files in a game that could potentially contain CMI that could get stripped in the reverse-engineering/re-compiling process. Perhaps a slim one, from the way you describe it to me, but one with potentially sizable consequences.

Dan Rosenthal
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Jonathan: don't be so quick to laugh at the DMCA. Any company that wants to do business in America can't argue with it, and as I understand most of the rest of the (industrialized) world is looking at adopting its provisions under the ACTA treaty, that's not counting the ones that already exist under WIPO, WCO, as well as your many national laws, possibly even your own. Taking a cavalier attitude towards reverse-engineering is simply inviting trouble. Laugh at us Americans all you want, but by next year you'll also be laughing at the EU/EC, Japan, Korea, Australia, Canada, and a half dozen other countries. Where would you distribute your newly reverse-engineered game then?

Wyatt Epp
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OT @Jonathan,

Yes, it does lack frills, but it's completely sufficient for this exercise. The goal was to quickly teach a professed non-programmer the difference between normal code and assembly, and he says the goal was accomplished. This is also why I went with pure C and the write() syscall rather than something more "friendly". (C++ is not my friend, and I will not be letting it see my privates. ;) )