John Lumsden Donaldson, 61, is well aware of what those organisations have been going through.
His business was "virtually closed down for 24 hours" when he was the victim of a similar attack.
And it was only the efforts of his computer programmer son Mark which got his business back up and running.
"It's not just the big companies that have been attacked," John told the BBC.
"We were attacked on Thursday 4 May."
When John opened his doors that day as usual, he had little idea of the problems that lay in store.
He runs an auction company in Spain, where he lives in Formentera del Segura. It is a small business, employing fewer than ten people.
"None of the software would work on our network of computers in the office," he said.
"I thought my son might be updating the network."
He rang his son to check.
"Within five minutes he rang back and told me to unplug the servers and close down the system.
"He said we were being hacked."
John's business had been targeted with ransomware - software which infects vulnerable machines, locks data away and demands payment to unencrypt those files.
"They didn't take anything from us. They just wanted $500 (Â£390)," John said.
"I said we should just pay. But my son said there was no guarantee they would unencrypt the files after we had paid and they might ask for more money."
John's business uses two servers in England and two physical servers in Spain. All four use Windows operating systems - those in England running the newer Windows 10; those in Spain using an older iteration of Windows Server.
"They locked up our system files so we couldn't run any of our software or access customer data. We could not pay our customers.
"I was worried about the security of our clients but they didn't access any of that part. It was our physical servers in Spain.
"They found a backdoor in Windows Server through our telephone line."
John and Mark worked overnight to resolve the problem.
"Even now we still have issues," John said. "According to my son it's all linked to old Windows software.
"I really felt for our customers. It was a bit embarrassing to say the least.
"Thank God I had my son."
By UGC and Social News team
Organisations worldwide have been scrambling to get systems back online after a massive ransomware cyber-attack.