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Defense Grid: The Awakening Part #1

With Steam having those amazing sales, I picked up Defense Grid: The Awakening for something like 2-3 euro. I was bored, so sue me. I found that it was actually a pretty funny game for a few hours and then I figured, what the hell lets start hacking :D

Started up Cheat Engine and started searching for some values. Interestingly enough this game had some unexpected anti-cheat mechanisms in place.

Anyways, I went through the usual tricks, search for the credits as a integer, float, double, etc. Funny enough it seemed it was stored both as a float and a double. But changing those values did not do anything to the ingame credits.

That got me intrigued, apparently this game was either using memory-encryption or some other form of anti-cheat mechanisms. I then remembered that the first level starts off with 0 credits and a bit later in the level you got 200 credits to finish the mission. So I put Cheat Engine to work.

A minute or so later I had the starting-credits and I saw something strange. The value at this pointer never went down and in fact (by killing enemies) only went up, regardless of the amount of credits I spent.

This got me thinking, if this value does not go down, another value must be somewhere in memory that keeps track of what has been spent. So started a new mission,searched for the amount of credits spent on towers and found the value that keeps track of the amount of credits that have been spent.

Now having two values in memory it was time to find out what static addresses point to these values so I can create a trainer for the game. This is where things got funky. Normally I would use the pointer-scanner in Cheat Engine and it'll quickly tell you what base pointer points to the value. However that would be too easy wouldn't it ;)

With that not getting anywhere, I used Cheat Engine's "what changes this address" only to crash the game seconds later. I should have known because its a Steam game, it has anti-debugger protection. So I booted up my VMware image with Syser and repeated the whole process.

I found out that the code-address changing was at 8BB1FCh, the instruction in question as "movss dword ptr [ebx+10h], xmm0", great.

As I was interested in base address of the value, I booted up IDA Pro Disassembler which has to be the best disassembler on the market at this moment. Only to find out that there was yet another protection in place, the executable had been packed by a PE Packer.

For 2-3 euro, I didnt expect this many protections in place, but it sure made hacking this game so much more interesting. Anyways, check out part 2 which will be posted later to find out a way to get around a PE Packer. Its only one of the possible ways, but its probably the easiest way.

Posted by: Da_Teach on Friday, January 1, 2010  •  Syser IDA Pro Cheat Engine Defense Grid

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