A cyberattack that crippled the computer systems of a hospital network affecting six hospitals in Vermont and New York last fall happened after an employee opened a personal email on a company laptop while on vacation, a University of Vermont Health Network official said Tuesday.

The email was from legitimate local business that had been hacked, Doug Gentile, network chief medical information officer told The Associated Press. The email contained an attachment that had the malware. When the employee returned from vacation and logged onto the UVM network through a virtual private network, the attackers were ready and launched the attack, he said.

“We have no evidence at all that UVM was specifically targeted. We just got caught up in a broad phishing attack,” Gentile said Tuesday.

VTDigger first reported how the attack happened.

The October 2020 cyberattack caused significant, ongoing computer network problems for the University of Vermont Health Network, affecting its six hospitals in Vermont and New York, officials had said at the time.

UVM figured out how the cyberattack happened a week or so later by going through detailed logs, Gentile said. It had called state and federal law enforcement immediately and the FBI was extremely helpful in the investigation, he said. The source of the attack was a criminal gang that the FBI is familiar with, he said.

“These people are virtual and they can be anywhere. Most of them are offshore, some place where our law enforcement can’t get to them,” he said.

At the time of the attack, UVM Health Network had blocked access to personal email for anyone who was on the network but had not yet extended that to the machines when they were off the corporate network, which it had planned to do this year, Gentile said. The same day, the FBI and two federal agencies warned in an alert that they had “credible information of an increased and imminent cybercrime threat to U.S. hospitals and healthcare providers.”

Since the attack, UVM has installed more advanced viral wall protection on all corporate assets and considerably tightened up its vpn access, he said.

“So we’ve made a lot of changes,” Gentile said.

The attack cost an estimated $50 million, mostly in lost revenue, he said.