How to reverse engineer unprotected C++ software

Apr '24 • Coding

Hello, I'm Alex and I've been reverse engineering for over 7 years now and have been professionally mastering C++. Reverse engineering is my passion, and I'm here to show you how to reverse engineer an unprotected C++ program.

First, I want to tell you that reverse engineering is not something you can learn within a week or two, this takes years and it can be complicated to professionals too.

So to start it off, you're gonna need 1 tool for this, which is X64Dbg, you can find it at https://x64dbg.com/. Once you're there download the zip and go through the process. Now, we'll need a software to reverse engineer, and the best website out there for this would be crackmes, you can find it at https://crackmes.one/. Search for a crackme, I'm gonna be using this one for the tutorial: https://crackmes.one/crackme/6346ef0933c5d4425e2cd843. Once you're there, download the program and extract it (the password is crackmes.one), once you have extracted it, open X64Dbg and load the file you downloaded. Now once you are in X64Dbg, on the assembly lines right click, go to "Search for" -> "All Modules" -> "String references", once you are here, wait for the whole reference list to initialize, now once you're there, search for what it says in the program by firstly opening the program, in this case you're gonna wanna search for "this is the ultimate of simple crackmes, this will probably be way too easy, but can you find the password? ", and when it's found you should see the assembly lines again, now if you see the line that says "wrong, try again, (hint, try to decompile the code and look at the main function)", and once you're there you should take the address where it says "correct, nice job" by right clicking on the line and going to "Copy" and then going to "Address", once you've done that the address should be copied and you should get something like this: 00007FF6A091161E, now, go back to the "wrong, try again" assembly line and press space, once you're there remove everything and write "jmp 0x0007FF6A091161E" (make sure to add the x), and once you've done that, press "OK" then close the window, now go to the patch icon above, and click on it, then press "Patch File" and store it with whatever you want but make sure the name has the file extension ".exe" and once that's done, open the program's patched version, and write something random, and now, with whatever password you choose, you should be getting the "correct, nice job" message.

And that's pretty much it, if you need help feel free to ask for it in the comments section. Please keep in mind this is for unprotected programs and this won't work on games and other stuff, but you can learn more from this tutorial and I hope this made you want to reverse.

Good luck.

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