Ransomware, which holds a computer "hostage" until money is paid to give back the information, is being blamed by Microsoft and Russia on the National Security Agency. The virus is believed to be built upon leaked NSA software.
The hackers disseminated their WannaCry virus by exploiting a vulnerability patched by Microsoft in March, but as they no longer support XP or 2003, computers running those systems were vulnerable.
Add in businesses that don't stay current on their virus patching and you have an open window for hackers. It only takes one unpatched computer per network for the malware to spread. A patch is a piece of software that updates or improves a program. In this instance, a patch would improve the security of a machine.
The hackers requested the $300 per computer ransom be paid via Bitcoin, which is not traceable. Microsoft released some additional patches over the weekend prevent themselves from being victims of further attacks, and Barthold recommended that everyone update their computers.
He also recommended having strong antivirus and anti-malware programs that update in real time. The anti-virus software is only as good as it's managed, though, lest you be forced to pay the ransom, as the FBI has recommended.