The underlying architecture of a computer can be a tricky thing. There are many levels that you have to account for. You have the hardware level, which is the stuff that you see on the motherboard. For example, the CPU, the memory, and all of the other components that you see when you open a computer. Then on the software side you have two levels -
The Application level, which is the side that you see when you are using the computer. This is the part that you interface with everyday. The GUI of the OS and the actual programs that you use.
And then you have the Kernel level. This is where the code that makes the operating system work with the hardware, resides at. You merge all three of these areas and then you have a working computer.
When you are a hacker, both white hat and black hat, you know these areas intimately. You study how this all works so that you can manipulate it to do what you want it to do. This is why operating system vendors must think of tricks that will allow them to thwart the bad guys. One of these tricks is known as ASLR.
ASLR is also known as Address Space Layout Randomization. What this means exactly is kind of difficult, but we will walk you through it slowly. As we showed you earlier in the article, the computer is made up of many different layers that work together. One the ways that these layers work together is when you start up a program. When a program starts, even the operating system itself, it is taken off of the hard drive and placed into the memory. So once it is placed into memory, it is then mapped with what is known as the address space. When a program runs, also called a process, it loads certain pieces into this address space.
Before ASLR, a hacker would know which pieces would be put into certain address spaces. So in any attack that they would do, all they had to do was to remember the address space of that piece of the program. Then they could run the attack. To make this harder, the operating system vendors made the place that they would put pieces of the data random. This is where ASLR comes in. Now an attacker does not know ahead of time where the pieces are going to be at. They have to either guess or find some way around it. This is possible but it is not easy to do. It makes the path of exploiting the system a lot harder than it would normally be.
With ASLR added to Windows 7, it makes the system a whole lot safer than past operating systems. Now attackers have to come up with a lot better exploits in order to be able to take over the system.
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