braiden

How do you crack executables?

13 posts in this topic

Hi all,

Ive inevitably needed cracked software for various things, and im wondering, how would I best begin cracking executables. Just simple things like a dvd-check bypass on some games I own. Anything that would get me started really :)

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Do you know assembly language, that would be a good start. Seriously, cracking games can be quite hard. You need other skills first, being a competent assembly language programmers most important.

There are a lot of challenges here though. In a nutshell, all you have to do is disassemble the software (and hope they left the symbol table intact) and find where the CD check is done. Once you find that, find what parts of the software call that function and NOP them out. The game developers make it really, really hard on you though. Multiple checks in multiple places, dummy checks that, when removed, cause the game to crash and things of this sort.

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Hmm, I dont know assembly very well at all. The furthest I've gotten into it was using Debug on a XP machine to crack the bios.

So basically, from what im gathering, its:

1. Find check calls

2. Find return true calls

3. Replace return false with return true?

4. Do this with assembly and an Exe Decompiler?

Btw, just to be simplistic, im using Diablo 2 as the exampler game I would like to try to crack.

Edited by Spooned
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More or less, yeah. But there are almost always curveballs. Especially on a big-name game like Diablo II. Then again, some don't even bother and the checks are nonexistent or simple.

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Just for a more general look of things, using Securom as an example, what sort of checks do they employ on executables?

Also, do you know of any decent Disassemblers that I could use?

(note the lack of googling, not trollin, just not sure of what to google for :P)

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I used to use OllyDBG, very nice.

There's another really old one that's really good, I forgot the name of it... I want to say blackice but I am pretty sure that's that firewall that got bought by a company.

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Your thinking of softice. A bit hardcore for cracking a game but still a nice tool to have around. Looking at dissasemblers such as ida pro would be a good start. In terms of actually cracking software the basic idea (as Ohm said) is just to bypass the checks, but a lot of developers have lots of nasty tricks up their sleves (even going so far as to encrypt parts of the code). Luckily for the software crackers alot of these techniques are recycled from other products. A good book on disassembling is "Hacker disassembling uncovered" by Kris Kaspersky. I never got the the end of it (other things came up) but i definitely plan to some day.

edit:

Oh yea, OllyDBG is pretty good as well

Edited by phr34kc0der
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Me being the person I am and never having enough time to put in alot of effort in a subject like this. If your goal is to say... Play a game with no need for a cd I found a useful thing can be finding an already modified .exe. But shame shame on pirating if thats your goal :-D Of course youd have to be careful with the source of the .exe, could be a sketchy file. In my case yesterday. I had counterstrike installed on my system and it deteted wine and wouldn' t let me play the game for "Disc EmulatorSoftware Detected" reasons. I dont know, the whole subject confuses me in all honesty. I talked to a friend that I knew and he gave me the CZero.exe and I replaced it with mine and no need for a cd anymore. In my case I don't believe it was illegal because I had the original disc.

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Lol, for discussion sake, Diablo II has built in play-without-disc functionality, via the official patches. I just want to learn something thats awesome.

Thanks guys, Ill have a look and post /how I made of any cracks i make work :P

Edited by Spooned
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Just a heads up, i think that actually posting cracked software is illegal. Posting the patch files, however, is not.

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Cool, thanks man. I knew it was illegal, just misworded my sentance a bit ^_^""

Anyhow, just looking at the Diablo II exe.... Wow, so many fake checks in there... or atleast from what I can tell.

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I have a ton of resources for you if you would like:

http://www.tuts4you.com/download.php?list.29 - a set of ollydbg tuts. The site they are on has a lot of cracking in general info.

http://www.woodmann.com/krobar/ - this site has some diablo stuffs on it. Here is good too.

a process monitor and a registry monitor are invaluable tools.

A possibly good resource for said crack, would be to look at the EXE that has already been cracked. Kind of like a tutorial...

http://gamecopyworld.com/

On the disassembly side of things, which one you choose is up to you. For the most part its a matter of preference. A good hex editor helps.

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