by Joshua Mccracken

Created on: May 29, 2009

Computers require memory to function. They require both bandwidth and memory to function on the internet. Data storage, often called memory, refers to computer components, devices, and recording media that retain data used. If the computer cannot store the information to run a program in memory, the program stops responding and simply doesn't run. Denial of service attacks disrupt communications either by disrupting a computer's ability to communicate over the internet, by disrupting an application's ability to communicate with the operating system, or by disrupting the operating system's ability to function. In it's simplest form a denial of service attack can be a malicious applet designed to crash a web browser. Below I will explain what constitutes a denial of service attack and how they are perpetrated.

The simplest sorts of denial of service attacks can be exploited over a network without interaction from the victim, in many cases. For example, when you use that beloved file-sharing program that thousands of other people are using, the program will often open a port or 'virtual doorway' that accepts incoming communication in order to transfer files that you are sharing from your computer. If the program is vulnerable to a buffer overflow, it can be exploited remotely to run shellcode that can destabilize the operating system causing it to cease to function. In most cases like this we can fix this with a simple reboot, provided your vulnerable software is not still running when the computer restarts. Though this form of denial of service attack is spoken of less in the media, it is actually extremely common.

The most well-known forms of denial of service attacks (DoS) are known as distributed denial of service attacks (DDoS) because they typically involve multiple computers compromised by malicious individuals. Affected computers are known as 'zombies'. In this case, DDoS disrupts communication by flooding targets with junk data. Bandwidth is not really something that is intangible. It is actually physical because even our fiber optic cables have limits as to how much data can be sent or received at any given time. Since internet service providers have these limitations even on a backbone where there is the most bandwidth, these constraints are passed on to the end user. Flooding a target with excessive junk data disrupts communication by filling a connection to capacity leaving legitimate communications unable to reach their intended destination. Back

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