November 2, 1988. Robert Morris, who was a student at Cornell University, launch his worm in the Internet around 6 P.M. The worm was originally designed to measure the size of the Internet. Exploiting some flaws in the sendmail MTA and in the finger service, it got access to vulnerable systems, self-replicating and jumping to other connected systems thus spreading all over the net. The problem was that it didn’t check if the system had been infected already, so many systems were infected more than one time, running several worm processes that wasted all the system resources, slowing the machine down, and in many cases becoming totally unusable.
The attack affected to more than 60.000 servers, which was 10% of all Internet connected systems at that time. A lot of system administrators got scared, and unpluged their systems from the network, so the unavailable servers were more than just the infected ones. Could be said that this was the first Internet Denial-of-Service attack.
Nowadays, Robert Morris is and associated professor of computer since at MIT.