I read an intro article on hacking games via DirectX over at AltDevBlogADay. The essence of the techinques is to intercept the game calls to the DirectX API. Then you can substitute your own evil code in there. The most common of such hacks is the wallhack.
For the wallhack, you wait until a call is made to DirectX with the enemy's position. Then you literally draw a wall around them on the screen. I guess that traps the enemy in the wall. They can't get you or shoot you. Pwned.
Another hack you can do with an enemy location is to draw them a different color. For example, you could highlight all the bad guys in red. This will allow you to visually detect them easier, and shoot them up. Now doing things such as this might get you noticed. And if the game cops catch you, you might be banned. So you need to be sneaky. But that is a story for a future post.
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