![]() Printf("Inside Buffer Overflow function") īelow is the stack representation of a normal stack and a buffer-overflowed stack.īefore going into the Buffer Overflow stack, few important points about above stack are: ![]() Now let’s consider a simple program like the one below and its stack representation "" main() Whenever the CPU encounters a branch or a jump statement, the IP changes its value to a completely new memory location and then it will begin incrementing from the new memory location. With each fetch, this Instruction Pointer is incremented and new memory location is fetched. How does the CPU fetch the next instruction? It does so through the use of an Instruction Pointer that tells the CPU where to grab the next instruction from memory. When a program runs, the CPU fetches instructions from memory one by one. Before going a step deeper in the program, let’s refresh our concept of how a program runs on the computer. Now imagine that someone has issued a command and the data is spilling on it. Now you must be asking, “So what?” Only data is being spilled, after all. It will then move out into the adjacent memory locations. ![]() It is the same case with buffer overflow, which occurs when more data is added than a variable can hold. For example, when more water is added than a bucket can hold, water overflows and spills. Buffer overflow attacks are analogous to the problem of water in a bucket. What is buffer overflow?īuffer overflow attacks are considered to be the most insidious attacks in Information Security. Not only are we going to cover how buffer overflow occurs but also how to defend against these attacks. This article is Part One of the series, and will focus on Buffer Overflow attacks only. However, this article series will serve as the basic building blocks for those advanced articles. Articles we read on the web are usually at a very advanced level with a start by dancing down the stack. I have come across various analysts who want to learn how buffer overflow and format string attacks actually occur.
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