A malicious attack on a network resource that prevents legitimate users from accessing the resource, typically implemented by initiating an overwhelming number of spurious requests for service.
An assault on a network that floods it with so many requests that regular traffic is either slowed or completely interrupted. Unlike a virus or worm, which can cause severe damage to databases, a denial of service attack interrupts network service for some period.Distributed AttackA distributed denial-of-service (DDOS) attack can employ hundreds or even thousands of computers that have been previously infected. The computers act as a network of "zombies" working together to send out bogus messages, thereby creating huge volumes of phony traffic.In 2016, the Dyn DNS system was hammered by a DDOS attack that caused sporadic slowdowns of major sites such as Twitter, Netflix and The New York Times. The zombie traffic reached more than 100 gigabytes per second of bogus messages. See botnet, smurf attack, SYN flood attack, land attack, teardrop attack and Ping of Death.