Renault shut down several French factories after the cyberattack, and one of Nissan's United Kingdom factories was also impacted.
Hundreds of thousands of computers have been affected so far.
That raises questions about inequality in technology, said Stewart Baker, a former general counsel at the National Security Agency.
Microsoft has hit out at governments for "stockpiling vulnerabilities", blaming them for the "widespread damage" caused by the latest cyberattack. The NSA did not immediately return a request for comment. It effectively takes the computer hostage and demands a $300 ransom, to be paid in 72 hours with bitcoin.
Ransomware is a program that gets into your computer, either by clicking on the wrong thing or downloading the wrong thing, and then it holds something you need to ransom.
It's still not clear who was behind the attack. According to Business Insider, about 7% of PCs are still running XP, and nearly half are running Windows 7 (which is also soon reaching that window where its support will end).
Also, most large-scale ransomware campaigns typically generate a unique bitcoin address for each infection.
In this context it's perhaps worth remembering that previous year Apple came under tremendous pressure to create a special version of iOS for the US government, under the promise that it would never escape their safe hands and get into the wild.
Microsoft's chief legal officer Brad Smith has voiced direct criticism of the US National Security Agency for not revealing the details of the vulnerability that was at the root of the WannaCry ransomware. But he also said the incident was a "wake-up call" for governments.
"You can point a lot of fingers, but I think given that this was not a zero-day vulnerability (for which no patch is available), the people hacked are to blame", said Robert Cattanach, a partner at the worldwide law firm Dorsey & Whitney and an expert on cybersecurity and data breaches.
The cyberattack highlights how critical infrastructure and major organizations can be harmed by outdated software and technology.
In 2014, Microsoft ended support for the highly popular Windows XP, released in 2001 and engineered beginning in the late 1990s, arguing that the software was out of date and wasn't built with modern security safeguards.
Therein lies the uncomfortable irony for Microsoft.
This does indicate that attacks, both from the WannaCry authors and other cybercriminals, will likely continue and, despite patches being available, many systems will likely remain vulnerable for some time to come.
For a variety of reasons, that fix never made it onto the affected computers.
The attacks exploit vulnerabilities in old Windows operating systems. This includes Windows 7, Windows 8.1, and Windows 10; if you are running something older than this, the finger should be pointing at yourself. The company rushed out a patch on Saturday, however. "Software updates and security patches are pushed to us as needed so that we are using the most current approved versions of software on our computers".
Well, you don't have to, but there is now no way to fix a computer that's infected by WannaCry.
Complex software interacts in sometimes unforeseeable ways with its component parts, and this makes IT managers loathe to push updates without a battery of tests.
Most computer security companies have ransomware decryption tools that can bypass the software.
Other potential targets could be even more disruptive. Computer scientists estimate that for every 1,000 lines of code written, there will be between 15 and 50 errors.
A fifth of regional hospital associations in Britain's National Health Service were affected and several still had to cancel appointments on Monday, as doctors warned of delays as they can not access medical records. But from the perspective of the NSA, Microsoft is asking the signals intelligence agency to unliterally disarm, which it isn't going to do.
But some other technology industry executives said privately that it reflected a widely held view in Silicon Valley that the USA government is too willing to jeopardize internet security in order to preserve offensive cyber capabilities. Recovery from backups is one of them.