Magical gnomes present: Buffer Overflows and You
Is it the 90's? Are you wondering why your server is running slow? Why it's trying to ping flood some host in California? Why someone else is logged into your machine and you've recently become a prominent porn hosting provider? This site will help you figure it all out. And if you have a time machine, you can probably go back and do it to someone else!
Before continuing, it's important to note that this guide is designed for 64-bit systems. If you're trying any of these examples on a 32-bit machine, or even a 64-bit machine running a 32-bit kernel, you're probably going to run into differences.
There are also a number of prerequisites to understanding this material. You should be comfortable with C programming. You should be able to understand x86 assembly (you don't necessarily have to be good at writing it - it just shouldn't scare you). Finally, you should be familiar with Linux in general. Commands like chmod should be second nature to you.