<P> TDoS differs from other telephone harassment (such as prank calls and obscene phone calls) by the number of calls originated; by occupying lines continuously with repeated automated calls, the victim is prevented from making or receiving both routine and emergency telephone calls . </P> <P> Related exploits include SMS flooding attacks and black fax or fax loop transmission . </P> <P> Defensive responses to denial - of - service attacks typically involve the use of a combination of attack detection, traffic classification and response tools, aiming to block traffic that they identify as illegitimate and allow traffic that they identify as legitimate . A list of prevention and response tools is provided below: </P> <P> Application front - end hardware is intelligent hardware placed on the network before traffic reaches the servers . It can be used on networks in conjunction with routers and switches . Application front end hardware analyzes data packets as they enter the system, and then identifies them as priority, regular, or dangerous . There are more than 25 bandwidth management vendors . </P>

Which of the following is not a type of distributed denial of service attack