Interestingly, it doesn't even try to attack Windows 10, focusing solely on Windows 7/8 and earlier operating systems that are still vulnerable to the attack.
Once it's on a computer, it goes on locking up the user's files and arranging the ransom message.
That's because even without phishing links, another part of the exploit the searches out a vulnerable server component (SMBv1) on unpatched Windows machines and can infect them remotely.
This probably won't work across the internet for PCs behind a firewall or router, but if a server is connected directly to the internet, or a PC is on the same network as an infected computer, it can spread quickly -- which is exactly what happened yesterday.
So, why did I download Tinder and Bumble before boarding my flight Prague last August?
Perhaps it was a joke, or at least a social experiment.
However, as @Malware Tech Blog notes, anyone could modify the attack to remove the killswitch and begin attacking computers again.
Younger Czechs are likely to pay for their own expenses on a date.