What is WannaCry ransomware?

(FOX News) - The ransomware cyberattack known as "WannaCry" infected hundreds of thousands of computers globally on Friday, but the malware was first detected in March and publicly reported stolen from the United States National Security Agency a month later.

WannaCry is a ransomware virus that holds computers hostage until the user meets the demands. The WannaCry software infected computers operating on Microsoft and displayed messages demanding users to pay $300 in bitcoin -- type of digital currency widely used online. The required payment would typically double to $600 if the first ransom wasn't paid within days and, after a week failed action, all files on the infected computer would be destroyed.

The malware paralyzed computers in factories, banks, government agencies and transport systems, hitting 200,000 victims in more than 150 countries by Monday. It also hit a "limited number" of U.S. companies over the weekend, a senior DHS official confirmed to Fox News. CERT (Computer Emergency Readiness Team) worked with the affected U.S. companies and their European partners over the weekend to get a patch to parties affected by the ransomware infection.

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Though many first heard about WannaCry on Friday, Microsoft discovered it earlier this year and released a security update to patch the hole in its system on March 14, Brad Smith, Microsoft's president and chief legal officer, said in a blog post on the company site.

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The virus was able to infect many systems on Friday because some users didn't install the latest security update, leaving computers vulnerable for any attack. It takes just one click on an infected link or email attachment to have the virus spread to other computers within the network.