As cyber attacks become an increasing global threat, the healthcare industry is not prepared, experts warn.

“We’re going to have our digital D-Day, our cyber D-Day, if you will, in medical, and there’s going to be patients that die. It’s going to be a big deal,” said Christian Dameff, M.D., an emergency room physician and expert on cyber vulnerabilities, told the Sacramento Bee.

During a summit at University of Arizona College of Medicine, Dameff and others predicted scenarios such as hackers demanding ransom for electronic medical records.

Interoperability has its downsides, which is that many hospitals and accompanying centers, which could include a nursing home, make a large-scale attack more plausible. Hospitals also use 10 to 15 medical devices per bed, the newspaper reported.

“Cyberattacks are very scalable. You can go from one hospital to 500 hospitals with much less effort than it takes to attack 500 hospitals physically,” said Dameff. “You can see that these risks, they explode.”

Among recent cyber attacks have been the WannaCry ransomware attack in May that hit the U.K.’s National Health Service.

“Every time we see something successful like WannaCry and Petya, you see other actors learning from that rather quickly, and they are able to replicate that style of attack,” said Chris Wysopal, co-founder and chief technology officer at Veracode, a Massachusetts cybersecurity firm, told the Bee.

Providers should pay attention to older technology that is more susceptible to hacking, experts warned.