A Warhol Worm: An Internet plague in 15 minutes!
'...by simply changing the infection pattern, it is possible for a malicious programmer to build a "Warhol Worm", able to attack all vulnerable machines, worldwide, in 15 minutes. A reactive, human defense would fail before such an onslaught. It is an important exercise to realize just how vulnerable we are.'
Believable. Very believable.