Distributed Denial Of Service attack, launched with tools such as trin00, tribe flood network or stacheldraht.

It was reported that Yahoo was receiving data at the rate of 1 gigabyte per second at the peak of the ddos attack on it in February 2000. In future years this will sound trivial but currently this is an astounding amount of data. It really raises the question of whether the problem was just faulty network hardware.