Denial of service

Denial of service

A denial-of-service (DoS) attack involves certain forms of malicious damage to a computer system. Such an attack aims to prevent legitimate users from accessing computer services.

Perpetrators can generate a DoS attack in a number of ways. Three basic areas of attack exist:

the consumption of limited resources, such as bandwidth, disk space or CPU time
alterations to configuration information, such as routing information or registry entries
the physical disruption of networking components

Attacks on resources have become increasingly popular, mainly through attempts to "flood" a network with excess or spurious packet data over the Internet, thereby preventing legitimate traffic.

The distributed denial-of-service (DDoS) attack - a DoS attack where many computers work together to attack a target system - has also become widespread due to the efficient and available tools which can set up and launch such an attack.

The smurf attack forms one particular variant of a DoS attack on the public Internet. It relies on mis-configured network devices that respond to so-called broadcast addresses. Abusers will send large numbers of IP packets with a faked source address (set to the address of an intended victim, such as an IRC server). To combat Denial of Service problems on the Internet, services like the Smurf Amplifier Registry have given Network Service Providers the ability to identify mis-configured networks and to take appropriate action such as filtering.

DDoS attacks compare with the "Slashdot effect" that occurs when a website gets a sudden spike in traffic which its server cannot handle due to a popular website linking to it.

External links

Distributed Reflection Denial of Service