Talking technology - denial of service attacks

Amazon.com the online retailer, US news company CNN, and President Mikheil Saakashvili of Georgia are just a few of those to be targeted by high-profile Denial of Service (DOS) attacks - which occur when computers, networks, or websites are unable to respond to legitimate requests for information, resources, or services, because access has been deliberately blocked or disabled.

DOS attacks can be aimed at a range of services, including e-mail, e-commerce sites, and online banks, and they come in various forms. They may involve the destruction or alteration of configuration information or of the components on a network or computer system (of which more later), or the consumption of bandwidth, network connectivity, and other scarce, limited, or non-renewable resources. The latter approach, however, tends to loom largest in the public consciousness, because these are the commonest and most obvious attacks, as well as being the easiest to understand and to perpetrate.

Distributed DOS attacks, which attempt to flood computer systems, networks, and websites with so many requests for information that they become overloaded, are one of the internet's greatest weaknesses. They are perpetrated with the help of thousands of poorly secured computer systems that have been broken into, infected with software that turns them into 'slaves'.

If you want to learn more about the various forms that DOS attacks can take, the internet is awash with information. This ranges from news coverage of incidents and DOS approaches such as the 'nuke', 'teardrop attack', 'ping of death', 'smurf', and more, to white papers explaining the threats and how to deal with them.

Most DOS attacks create temporary problems. Even so-called 'permanent DOS' attacks (such as 'phlashing'), that can damage a system so badly that it requires the replacement or reinstallation of hardware, can be overcome. But the attacks can be very costly to commercial enterprises and other organisations in terms of inconvenience, lost revenue, damage to the corporate reputation, and criminal extortion - DOS attacks are increasingly perpetrated (and threatened) by organised criminals with a financial motive.

Unfortunately, there is no single magic bullet solution that will protect an organisation against a DOS attack, and resistance to attacks requires an approach that takes a variety of preventative measures. These can include the design, implementation, and support of systems, through tools such as anti-virus software and firewalls, to dedicated intrusion detection and prevention systems, and DOS mitigation systems.