Code Red was a computer worm that targeted Microsoft's IIS web server. It was the first large scale threat to successfully target enterprise networks and deface them.
Code Red - named after the Mountain Dew flavour as that's what those who discovered it were drinking at the time - spread itself around using a vulnerability known as a buffer overflow. It used a long string of the letter N to overflow the buffer, which then allowed the worm to execute its code and infect the machine. Typically, it would post a message to whichever website it affected stating it was "hacked by Chinese".
As the worm did not check to see if the server was vulnerable to its particular form of infection, it ended up running itself dry. After a 28 day window it petered out and hasn't presented many issues since.
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