Explain how a denial of service (dos) attack works. after describing a dos conduct some research and provide an example of a real company or website that was brought down by a dos. what was the motive of the attackers).

                                                                                   

A Denial of Service(DoS) is a cyber attack in which the attacker makes a machine or network resource unavailable to its intended users by temporarily interrupting services of a host connected to the Internet. It works by flooding the targeted system or resource with redundant requests or traffic to overload systems and prevent legitimate and valid requests from being accomplished.Usually the user establishes a connection by sending a request to server to authenticate it and server responses back by giving authentication permission. This permission is acknowledged by the user and then is enabled on the server.Contrary to this, in a DOS attach, users send multiple authentication requests to server and these requests contain wrong return addresses so server cant identify the user in order to send permission. The server waits for some time before attempting to close the connection but before it closes the connection the perpetrator sends new set of  false requests and this process starts again.DOS attacks can slow network performance, makes a certain website unavailable and not accessible.BBC was attacked with a DDoS attack measuring over 600 Gbps, The motive of the attackers who claimed responsibility, was that they were just “testing.”The biggest DDoS attack happened to target GitHub. This politically motivated attack lasted several days and adapted itself around implemented DDoS mitigation strategies. The DDoS traffic initiated in China and it is suspected that the Chinese Government oversaw the attack.Wikipedia was brought down by DDoS attack in Germany and some parts of Europe.  TalkTalk a company which provides pay television, telecommunications, Internet access, and mobile network services to  costumers in the United Kingdom was brought down by DDoS attack   by a group of teenagers purely for their own entertainment.In 2000 a 15-year-old hacker known as ‘Mafiaboy’ brought down several popular websites in the world including CNN,  eBay, and Yahoo, This attack had resulted chaos in stock market.  Attacker was revealed to be a high school student named Michael Calce, attacked by hacking into the networks of several universities and using their servers to perform DDoS attack. His motive was to intimidate other hacker groups.

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