Patch Everything

The place to start is with patching Windows machines immediately, according to cybersecurity firm Cybereason. In March, Microsoft had patched the "Eternalblue" exploit, an NSA-derived vulnerability that researchers say is the likely culprit in WannaCry.

Specifically, the attack exploits a flaw in the Server Message Block in Windows, which can enable remote code execution, Cylance said. Organizations that are behind on patches or running legacy operating systems, such as Windows XP, are vulnerable unless updates are made, Cylance noted. Microsoft is offering a rare patch for Windows XP in response to WannaCry.

Security experts say that along with patching the operating system, organizations should also patch third-party applications to secure against the ransomware attack.