An attack which attempts to block access to and use of a resource. It is a violation of availability. DDOS (or DDoS) is a variation of the DoS attack (see DOS) and can include flooding attacks, connection exhaustion, and resource demand. The distinction of DDOS from DOS is that the attack traffic may originate from numerous sources or is reflected or bounced off of numerous intermediary systems. The purpose of a DDoS attack is to significantly amplify the level of the attack beyond that which can be generated by a single attack system in order to overload larger and more protected victims. DDoS attacks are often waged using botnets. (See botnet.)