NEW YORK — Computers in companies, hospitals and schools around the world got stuck repeatedly rebooting themselves Wednesday after an antivirus program identified a normal Windows file as a virus.
McAfee confirmed that a software update it posted at 9 a.m. Eastern time caused its antivirus program for corporate customers to misidentify a harmless file. It has posted a replacement update for download.
McAfee could not say how many computers were affected, but judging by online postings, the number was at least in the thousands and possibly in the hundreds of thousands.
McAfee said it did not appear that consumer versions of its software caused similar problems. It is investigating how the error happened "and will take measures" to prevent it from recurring, the company said in a statement.
The computer problem forced about a third of the hospitals in Rhode Island to postpone elective surgeries and stop treating patients without traumas in emergency rooms, said Nancy Jean, a spokeswoman for the Lifespan system of hospitals. The system includes Rhode Island Hospital, the state's largest, and Newport Hospital. Jean said patients who required treatment for gunshot wounds, car accidents, blunt trauma and other potentially fatal injuries were still being admitted to the emergency rooms.
Deborah Montanaro of North Kingstown, R.I., told The Providence Journal her son was turned away by the hospital and not given the spinal radiation therapy he needed to treat his leukemia.
"It is impacting patient care," she told the newspaper. "They have no Plan B. I am very upset."
The hospital's computers came back online around 4:30 ET, Jean told the newspaper.
In Kentucky, state police were told to shut down the computers in their patrol cars as technicians tried to fix the problem. The National Science Foundation headquarters in Virginia also lost computer access.
Intel appeared to be among the victims, according to employee posts on Twitter.
"For PCs that have been affected and are in a state of reboot, Intel IT is still working on how to get the deleted files back on the operating system, which will allow PCs to boot normally again," spokesman Bill MacKenzie told The Oregonian.
"We do have instructions out that are working for some people and not for others. We are continuing to work the issue."
Peter Juvinall, systems administrator at Illinois State University, said that when the first computer started rebooting it quickly became evident that it was a major problem, affecting dozens of computers at the College of Business alone.
"I originally thought it was a virus," he said. When the tech support people concluded McAfee's update was to blame, they stopped further downloads of the faulty software update and started shuttling from computer to computer to get the machines working again.
In many offices, personal attention to each PC from a technician appeared to be the only way to fix the problem because the computers weren't receptive to remote software updates when stuck in the reboot cycle. That slowed the recovery.
It's not uncommon for antivirus programs to misidentify legitimate files as viruses. Last month, antivirus software from Bitdefender locked up PCs running several different versions of Windows.
However, the scale of this outage was unusual, said Mike Rothman, president of computer security firm Securosis.
"It looks to be a train wreck," Rothman said.
In Utah, at least 700 of Utah Valley University's 5,000 computers on campus were affected, but university spokesman Chris Taylor said all computers were back up and running by noon Wednesday, as IT officials "were right on top of it."
In Sarasota County, Fla., school district officials said about 800 computers experienced the problem, and power was pulled quickly on the PCs. Officials said they were able to get computer systems up in running again in a little more than half an hour.
Msnbc.com’s Bob Sullivan and The Associated Press contributed to this report.