[[SLIGHTLY OFF-TOPIC FOR THE LIST]]

Some quick notes:
1
If you are interested in the worm mechanism spreading
the infection, there's a good article here:
https://blog.malwarebytes.com/threat-analysis/2017/05/the-worm-that-spreads-wanacrypt0r/

2
You may adopt FOSS for many good reasons, but security
is not one of them. Unpatched vulnerabilities in critical
FOSS pieces have lived for years. E.g., 'Dirty Cow'
(CVE–2016–5195) was sitting unnoticed(?) for nine
years; the bug causing CVE-2015-7547 glibc vulnerability
was around for 8 years, etc.

3
As ecosystems show, diversity is A Very Good Thing™.
However, diversity in the critical Internet infrastructure
is actually very poor. A critical exploit affecting Cisco core
routers may bring the Internet to its knees... and there is
nothing we can do in a highly concentrated, quasi-monopilistic
market.

Regards,

Enrique