what is dos attack

A denial-of-service (DoS) attack is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to a network. This can be achieved through flooding the target with traffic, sending it information that triggers a crash, or exploiting vulnerabilities that cause the target system or service to crash. There are two general forms of DoS attacks: those that crash services and those that flood services. The most serious attacks are distributed, known as Distributed Denial-of-Service (DDoS) attacks, which occur when multiple systems orchestrate a synchronized DoS attack to a single target.