Denial of Service

A Denial of Service attack (abbreviated DoS) is a malicious act of overloading or breaking a resource such that legitimate users of that resource are no longer able to access it.
One common form of DoS attack is the Distributed Denial of Service (or DDoS) attack which utilises a multitude of distributed agents to attack a single point of failure. For example, a large number of PCs may be infected by a virus or worm which is programmed to make many frivolous requests to a particular website, in order to overload the site so that it becomes unavailable.
There is also the Distributed Reflexive Denial of Service (or DRDoS) attack, in which these bots ping computers with large pipelines with spoofed IP address, in hopes all these computers will send a response to the spoofed source.

Some types of Denial of Service attack include:

• Bandwidth Consumption - a common form of attack whereby a machine is swamped with network garbage, preventing real data from getting through.
• Resource Starvation - an attack by a user of a local machine whereby a program is written to utilise as much memory, CPU time or disk space as possible.

External Links

Steve Gibson on DoS/DDoS/DRDoS Attacks (www.grc.com)