What is denial of service?

This is an act by a criminal, who floods the bandwidth of the victim’s network  or fills his e-mail box with spam mail depriving him of the services he is entitled to access or provide.

This act is committed by a technique called spoofing and buffer overflow.  The criminal spoofs the IP address and flood the network of the victim with repeated requests.  Since the IP address is fake, the victim machine keeps waiting for response from the criminal’s machine for each request. This consumes the bandwidth of the network which then fails to serve the legitimate requests and ultimately breaks down.

The diagram below will give you an idea of how the attack happens