CANBERRA, Australia — The world’s largest meat processing company has resumed most production after a weekend cyberattack, but experts say the vulnerabilities exposed by this attack and others are far from resolved.

JBS notified the federal government the ransom demand came from the ransomware gang REvil, which is believed to operate in Russia, according to a person familiar with the situation who is not authorized to discuss it publicly.

JBS hasn’t discussed the ransom demand in its public statements. Phone and email messages seeking comment were left with the company Wednesday.

JBS said late Tuesday that it had made “significant progress” in dealing with the cyberattack and expected the “vast majority” of its plants to be operating on Wednesday. The attack affected servers supporting JBS’s operations in North America and Australia. Backup servers weren’t affected and the company said it was not aware of any customer, supplier or employee data being compromised.

“Our systems are coming back online and we are not sparing any resources to fight this threat,” Andre Nogueira, CEO of JBS USA, said in a statement.

Ransomware expert Allan Liska of the cybersecurity firm Recorded Future said the attack on JBS was the largest yet on a food manufacturer. But he said at least 40 food companies have been targeted by hackers over the last year, including brewer Molson Coors and E & J Gallo Winery.

Food companies, Liska said, are at “about the same level of security as manufacturing and shipping. Which is to say, not very.”

The attack was the second in a month on critical U.S. infrastructure. Earlier in May, hackers shut down operation of the Colonial Pipeline, the largest U.S. fuel pipeline, for nearly a week. The closure sparked long lines and panic buying at gas stations across the Southeast. Colonial confirmed it paid $4.4 million to the hackers.

JBS is the second-largest producer of beef, pork and chicken in the U.S. If it were to shut down one day, the U.S. would lose almost a quarter of its beef-processing capacity, or the equivalent of 20,000 beef cows, according to Trey Malone, an assistant professor of agriculture at Michigan State University.

David White, president of the cyber risk management company Axio, said the U.S. has no cybersecurity requirements for companies outside of the electric, nuclear and banking systems. That may put companies like JBS and Colonial Pipeline more at risk.

White said regulations would help, particularly for companies with inadequate cybersecurity programs. Those rules should be sector-specific and should consider the national economic risks of outages, he said.

But he said regulations can also have an unintentional negative effect. Some companies might consider them the ceiling for how they need to manage risk, he said,

“Bottom line: regulation can help, but it is not the panacea,”’ White said.