On Sunday, union representatives for a Renault auto plant in France received text messages from the management: Tell the workers to stay home the next day. The company was still dealing with the fallout from a global hack that hit thousands of businesses and the factory would be shut.
Since the hack was first detected on Friday, the company’s technicians have been racing to assess the damage. They have cleaned and rebooted systems that control robots on Renault’s factory floors, trying to make sure their systems were back to normal.
As universities, hospitals and businesses around the world continue to take stock from a global hack that has locked up at least 200,000 machines since last week, they are going through much the same process. Many are also trying to determine if they have lost any data or if their systems are safe. Some are trying to figure out whether they should pay the ransom, or whether they have backups that will allow them to avoid giving in.
On Saturday morning, technicians inspecting computers at Renault’s Sandouville operation in northern France found a demand in French for a $ 300 Bitcoin ransom with a threat to erase data. The carmaker decided not to pay.
But Renault will face other costs from shutting factories. Production is slowed, for example, and it will need to pay partial unemployment insurance for the thousands of employees at the Douai site who were not able to work on Monday.
The fallout for companies and institutions is growing by the day. The hack spread to thousands of additional computers on Monday, largely in China, India and Russia, although the pace of the rogue software’s advance appeared to be subsiding, at least temporarily. The attack is even causing consternation at companies not affected so far, as they shore up their own defenses — and leaving them feeling more relieved than reassured.
“It’s a battle we’re fighting every day,” said William Caraher, chief information officer at von Briesen & Roper, a midsize law firm in Milwaukee.
“We live in this world where any email attachment could be carrying malicious software that could go viral,” he said.
Gauging the extent of the disruption globally is difficult. Some companies report attacks, but many do not, fearing potential damage to their corporate reputations. For some, the modest $ 300 ransom is an incentive to pay and move on, said Greg Young, an analyst at Gartner.
In Germany, the hackers’ ransom demands popped up over the weekend on the screens of ticket vending machines of Deutsche Bahn, the national railway. On Monday, Deutsche Bahn technicians were still working to remove the malware, and some vending machine screens were displaying plain text advising travelers to get information elsewhere — on the railway’s website or smartphone app.
But Deutsche Bahn emphasized that the hacking had no effect on its train service or signaling systems. And like many other organizations affected by the hack, the railroad was hoping the worst was over.
In the United States, FedEx, the giant package shipper, which had been hit in the attack that began on Friday, said that it had “resumed normal operations” and that its computer systems were healthy again.
In Asia, though, some of the challenges are just beginning. China alone reported disruptions at nearly 40,000 organizations, including about 4,000 academic institutions, figures that experts say are most likely to be low estimates, given the prevalence of pirated software there.
The list of affected organizations includes two of China’s most prestigious institutions of higher education, Tsinghua and Peking Universities; a movie theater chain in South Korea; and blue-chip companies in Japan like Hitachi and Nissan, which emphasized that their business operations had not been impaired.
China’s state-run oil company, PetroChina, confirmed that the attack had disrupted the electronic payment capabilities at many of its gas stations over the weekend. By Sunday, 80 percent of its stations were functioning normally again, it said.
In Britain, where the attack was first detected on Friday, the National Health Service struggled to get hospitals, clinics and doctors’ offices fully operational. The attack had caused some patients to be turned away from emergency rooms, and surgical procedures and medical appointments needed to be rescheduled.
In Sandbach, in northwest England, John Cosgrove, a 42-year-old general practitioner, said things were recovering, but he still did not have access to complete patient records. And the public seems to be putting off medical care that can be postponed until the N.H.S. computer systems are up and running normally again.
“On Friday, there was a feeling of chaos,” Dr. Cosgrove said. “But there are not many people booking to see us. It does feel quite different still.”
Until computer security experts closely examine infected machines, they will not know the mechanism by which the malicious software got into the computers and then spread.
The malware used by the attackers was sophisticated, security experts say, but the collection mechanism was not, by the current standards of ransomware, said Caleb Barlow, vice president in change of threat intelligence for IBM.
Some perpetrators include instructions for how to pay by Bitcoin — and even examples of people who paid and regained access to their data, and those who did not. But this global ransomware attack did not include such payment-easing features, Mr. Barlow said, and may account for the modest level of estimated payments so far. “That is a bit of a head-scratcher,” he said.
The Bitcoin payments as of late Monday afternoon were just under $ 60,000, according the Chainalysis, a Bitcoin analytics firm. The largest transaction was $ 3,300, said Jonathan Levin, co-founder of Chainalysis, suggesting that large corporations and government agencies have not been paying.
The cyberattack underlines the growing problem of ransomware.
IBM’s security research unit collects and monitors about 45 million pieces of spam a day worldwide. In 2015, less than 1 percent of the spam was ransomware. By last year, 40 percent had a document or web link that activated ransomware, and the current attack threatens to lift that percentage higher.
On Monday, Robert A. Iger, Disney’s chief executive, told employees at a town-hall meeting in New York that hackers had contacted the company to claim access to one of its unreleased movies and had demanded a ransom. Mr. Iger, who did not identify the film, said that Disney is not paying and has been working with federal investigators to resolve the matter.
It was not clear if a Disney film had actually fallen into hackers’ hands or if the attack on Disney was related to the one over the weekend. A Disney spokeswoman did not respond to queries.
Correction: May 15, 2017
An earlier version of this article misstated the direction of Chinese internet security stocks in the wake of the ransomware attack. Trading was suspended in these stocks after they rose, not fell.