"WannaCry is a type of ransomware that spread around the world last weekend, affecting more than 200,000 victims, including hospitals, in at least 150 countries, according to news reports. [...] WannaCry spread quickly in part because it was self-propagating, said Omar Chowdhury, assistant professor of computer science at the University of Iowa. Once it affected one computer, WannaCry would use a worm to look for other computers on a network it could infect. [...]
The UI’s Chowdhury said businesses may not install updates due to the cost or concerns that patches will mess with their systems. Short-term pain, though, is better than long-term consequences, he said. 'Even though it might break functionality for a limited amount of time, it’s a good idea,' Chowdhury added."