Today, computer worms and viruses (also called bugs) are recognized nuisances that have cost companies and even governments millions of dollars in terms of prevention and damage control.

But interestingly, the computer worm was once thought as an ally. When computers were bulky and generally inefficient—think large rooms full of connected mainframes—programmers had to worry about how to check which computer was “free” to handle a task. So worms would travel through the network, doing a “spot check”. It was only later that this technology was abused.

Viruses, on the other hand, were malicious from the start. Programmers invented a game they dubed Core Wars, that replicated whenever it was played until it took over the computers. Their goal was to make money from the repair software.