Dos Attack is a shorthand term for 'denial of service attack' and it takes advantage of the tcp/ip protocol in order to render online computers unusable. Denial of service attacks are an old and widely known hacking technique: simple put, it is when a hacker/hackers will attempt to flood a server with requests, or, will attempt to disrupt the operation of a servers software or physical hardware. The result of a successful denial of service attack will cause a server to shutdown due to an inability to handle any request demanded of it. Denial of service attacks usually result in one of three things happening:
Denial of service attacks are hard to defend against - especially when conducted by multiple users - which is highlighted by the 'Anonymous' hacking group who have successfully targeted a number of intelligence agencies with a cyberattack (2010-2013).
Denial of service attacks vary in the technique they employ when attacking a server. However, as the Internet and the servers which are connect to the Internet use the Internet protocol suite: the most obvious denial of service attack will use data packets in their attack technique. Data is transmitted on the Internet in data units called packets. Sophisticated denial of service attacks will attempt to disrupt the operation of a servers software/hardware by exploiting bugs within the servers software, or, within the software's configuration. This disruption, however, is usually by flooding/spamming the server with some form of request.