Denial Of Service Attacks

A denial-of-service attack (also, DoS attack) is an attack on a computer system or network that causes a loss of service to users, typically the loss of network connectivity and services by consuming the bandwidth of the victim network or overloading the computational resources of the victim system.
A DoS attack can be perpetrated in a number of ways. There are three basic types of attack:
1. consumption of computational resources, such as bandwidth, disk space, or CPU time
2. disruption of configuration information, such as routing information
3. disruption of physical network components

Attempts to "flood" a network with bogus packets, thereby preventing legitimate network traffic, are the most common form of attack, often conducted by disrupting network connectivity with the use of multiple hosts in a distributed denial-of-service attack or DDoS.

In a distributed attack, the attacking computer hosts are often personal computers with broadband connections to the Internet that have been compromised by viruses or Trojan horse programs that allow the perpetrator to remotely control the machine and direct the attack, often through a botnet. With enough such slave hosts, the services of even the largest and most well-connected websites can be denied.

Denial of Service attacks can also lead to problems in the network 'branches' around the actual computer being attacked. For example, the bandwidth of a router between the Internet and a LAN may be consumed by a DoS, meaning not only will the intended computer be compromised, but the entire network will also be disrupted.

Google for Related Stuff: