(You may or may not be joking; let's assume you're not for this response.)
This is a dangerous argument.
I'm a free software activist, and I firmly believe that security without free software is a facade, but that doesn't mean that free software is more always more secure; it's an open source argument that's been fairly easily refuted lately with high-profile bugs in software like OpenSSL.
It's easier to hide secrets in proprietary software, but most security vulnerabilities are bugs, not explicit backdoors. So even bit-for-bit reproducibility won't defend you against that.
I'm not saying you shouldn't use GNU/Linux---I think that every user deserves an operating system that is fully free, and hope that people will use it (or another free/libre OS). But my argument is on the basis of freedom, which still stands _regardless_ of security. It just so happens that I believe that strong confidence in the security of a system is not possible with proprietary software.
So far this year, Windows leads the scorecard regarding mass infections and business downtime due to them.
So while indeed, open source is not a guarantee for better security, the results are in its favor. It might also be because it's not such an attractive target to hackers due to its low share in the desktop market. But still there millions of linux servers online 24h/24h and I assume they have a bigger potential for monetisation.
Windows also leads the score card in installation base, which I think is the real causal relationship. If Linux was installed on 90% of desktops you better well believe there'd be a similar number of exploits for it. Something similar happened to Mac OSX not too long ago, as they grew in popularity more and more exploits were found for the operating system.
That's what I tried to express above. I was also wondering what is more profitable in the ransomware economy: infect many, almost worthless machines? Or infect an order or two of magnitude fewer machines, but with a higher chance of paying?
I'd say with a higher chance of paying because people administering them are more likely to know how to buy bitcoins, how to send them and what to do with the decryption key.
Or maybe Linux/Android on the desktop? Maybe all the PCs out there used for cash registers,ATMs, etc will run locked down Android systems in the near future instead of Windows.
The average Android phone probably has more spyware than the average windows machine these days. Probably a lot more vulnerabilities too because they rarely if ever get patched. Even the best android phones are only patched for 2 years.
Linux maybe more secure, but android is a ticking time bomb.
