Tag Archives: protection

19 Jul 2022

How security plugins for Autoplay Media Studio fail

Every once in a while I encounter a strange anti-reverse engineering protection. Protection authors are so focused on improving one specific aspect of the protection that completely overlook other, much easier ways how the system can be defeated.

Their logic is like this - someone stole my code, I better protect it. I've heard that cryptography is good, so I'll use that. Oh no, someone stole my code again! Let me add another layer of encryption over it! Few days/weeks/months later - Those bloody hackers won't stop! Let me protect my encryption code with another encryption!

Facepalm.

What the authors should do instead is stop and think. What do I want to protect? Against whom? For how long? What kind of loss is acceptable to me?

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13 Apr 2019

Unity3D protection in “AU2” dance games, part 2

Last December I wrote a blog post explaining how some of the AU2 dance games were protected. Apparently, the protection author read the blog post and updated his protection. smile This blog post will explain how the protection was changed and suggest several ways of dealing with the new features.

This analysis covers:

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29 Dec 2018

Unity3D protection in “AU2” dance games

Today's story is about dancing games. Specifically, about

These games employ some tricks in the APK file structure as well as modified libmono.so. I will go through each of the protection mechanisms step-by-step and explain how it works. In the end, you will have all the necessary information to implement your own decryption tool that can decrypt AU2 protected DLL files.

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31 Oct 2018

Unity3D, Mono and invalid PE files, part 2

In the first part of the series I explained how some cheat authors try to protect their work against other cheaters. It was a quick introduction to Unity3D and bugs in Mono that cheat authors exploit.

Last week someone emailed me another example of a game cheat. My tool from the previous article failed to fix invalid metadata, so I decided to look at it again.

Cheats by BlackMod.net

The cheat I received was made by Mod4U from BlackMod.net team. It appears that Mod4U is one of the most active members of the team, judging by number of the releases. His/her cheats use invalid PE file tricks and are encrypted, as you'll see later in the article.

After looking at different mods from other team members, I've confirmed that Rito, Aurora and Legend also are using invalid PE files for hiding their work. But none of their cheats encrypt Assembly-CSharp.dll.

So, let's look at the cheats and see what new tricks BlackMod team members have found!
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15 May 2018

Unity3D, Mono and invalid PE files

Some time ago, Reoto asked a very nice question on Black Storm forum:

Can someone fix the .dll (.net) pe header to MS DOS?
How can I do that?
If you know about protecting .net files for Android, please help me.
I have another question.
Can I fix dnspy to resolve .dll pe header isn't .net?

Obviously, English is not author's first language but it seemed like an interesting problem, so I decided to look into it.

Here is one of the files in question: https://mega.nz/#!0g4VHaIR!KmpQirte4_3lv8MSxyjETiufjFGb-CITpFGrXwxSgGY

TL;DR: Mono loader used by Unity3D accepts invalid PE files. It can be used to break most .NET decompilers. dnlib and tools based on dnlib (dnSpy, de4dot) were updated on 20-Apr-2018 but the rest of the tools still can't handle such files.
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