A distributed denial-of-service (DDoS) attack is a malicious attempt to disrupt the normal traffic of a targeted server, service or network by overwhelming the target or its surrounding infrastructure with a flood of Internet traffic. DDoS attacks achieve effectiveness by utilizing multiple compromised computer systems as sources of attack traffic.

DoS (Denial of Service) is an attack used to deny legitimate user's access to a resource such as accessing a website, network, emails, etc. Distributed Denial of Service (DDoS) is a type of DoS attack that is performed by a number of compromised machines that all target the same victim. It floods the computer network with data packets.