Ransomware also known as Wannacry is attacking again, but Windows 7 and Windows 10 operating systems with March and April updates fully applied appear to be immune. The computers being hacked are old versions of Windows 10, 8, 7 and XP that have not had security updates installed. XP is especially vulnerable.
Symantec, McAffee and any other virus protection provider are not required to tell you that you do not need their products to protect against these infections, and in fact, you probably should have a virus program.
If you are not encrypted, but have an outdated computer, consider using fixmestick.com, then applying updates, then installing Norton anti-virus.
For more sophisticated users, use Microsoft Defender or Security Center, plus Malware Bytes, as well as an occasional scan with fixmestick.
If you are not encrypted but cannot update the operating system, back up your data and either buy a new computer or reformat the hard drive. If fixmestick cannot get the virus out of the computer, or the Windows Update program just will not run, the cost of remediation probably exceeds the cost of a new computer.
Wanncry struck about two months ago. The newest Petya is a very refined improvement of the virus. EternalBlue was first formalized by the US NSA for spying purposes. But if they had not formalized the code, someone else would have done the same. North Korea is known to have produced a variant that was less sophisticated.
The initial infection of NotPetya comes from an email phishing scheme, sometimes in a password protected Microsoft Word document. Then, using the EternalBlue exploit it can worm its way within private networks of vulnerable networks.
Another NSA project called EternalRomance may have code in NotPetya. NotPetya has capabilities that allow it to steal administrator passwords and use them to further replicate. However, using Microsoft password facilities best practices would appear to make this a less likely threat.