Advanced Filters, Creating Alpha-Numeric shellcode

had covered in the first article. I felt it necessary to move onto this

next and more advanced topic. In this article I'm going to show you how to

conquer a rather tedious - and ALMOST impossible task: creating shellcode

completely comprised of alphanumeric characters. "Why on earth would we

want to do this?" you may be asking yourself right about now. The answer is

simple. There are several filtering schemes out there being employed by

programs that ONLY allow alphanumeric characters to be passed into their

buffers. Many programmers/hackers will tell you these are impossible to

exploit. In a great deal of ways they are right, but for the most part they are

wrong. Creating alphanumeric shellcode is time-consuming, annoying, and

tiring. Most people simply give up due to the complexity of its creation and

just assume it to be an impossible task. This is why there is little other

documentation like this available to you out there on the net. But, we will go

onto cover this topic in thorough detail. By the end of this article you will

not only be able to create your own code with little effort. But you will know

exactly what obstacles your code will be facing and how to overcome them

when possible. There is one last note I should add before beginning this

article. Due to the complexity of this type of attack and the ratio of

shellcode/original-shellcode, this type of attack will almost never work

against a Windows host. The code covered in this article is intended only for

a Linux box running under an IA32 Intel processor.