Many, but not all, computer networks at schools, hospitals, local government agencies and businesses that were shut down and crippled for much of Wednesday by a McAfee software update appeared to be functioning again Thursday.
"Most are back up and running. However, lots are operating but not without glitches still," said Robert Housman of the Cyber Secure Institute, a private analysis and advocacy organization in Washington, D.C. "And a number of smaller businesses that don’t have IT staffs in house are still trying to get everything back up."
Corporate customers using Microsoft's Windows XP operating system with Service Pack 3 were affected by the glitch. (Msnbc.com is a joint venture of Microsoft and NBC Universal.) A software update posted by McAfee caused its anti-virus program to misidentify a harmless file, shutting down computers around the nation and the world. McAfee posted a fix on its site and apologized.
"In our ongoing efforts to protect our customers from a seemingly endlessly multiplying variety and volume of attacks ... we released (an) update file that clearly did more harm than good," wrote Barry McPherson, McAfee's executive vice president, on a company blog.
"Let me say this has not been my favorite day. Not for me, or for McAfee. Not by a long shot ...Mistakes happen. No excuses."
Chip-maker Intel was among those with some of its computers shut down because of the glitch.
"There were a limited number of our systems that were affected," said Intel spokesman Chuck Mulloy. "I don't know if we'll be 100 percent recovered by the end of the day, but we should be largely recovered."
Johannes Ullrich, chief research officer for the SANS Institute, a national organization that does information security training, research and certification, said he has not seen any "outage" reports tied to the problem.
"Most businesses seem to have gotten the message about how to clean up the problem and are well underway to take care of it — or they are too busy to tell us otherwise," he said.
Ullrich said the fix "takes a couple of minutes for each system that is affected. The big problem is that in most cases it can not be done remotely. Someone has to walk up to the affected system, reboot it in safe mode, apply the fix, and reboot it again. This can take a long time if the systems are not close to each other, or if there is only limited onsite staff."
John Pescatore, Gartner research vice president and a security expert, estimated about 10 percent of "corporate desktops" were hit by the glitch.
"Our numbers say Windows XP has about a 65 percent share of business desktops, and I’d estimate that SP3 is about a little more than half of that, so let's say about 35 percent," he said. "McAfee’s market share of enterprise desktops is in the 35 percent range as well, so essentially 10 percent of corporate desktops could be impacted."
The problem forced about a third of the hospitals in Rhode Island to postpone elective surgeries and stop treating patients without traumas in emergency rooms for much of Wednesday, but systems were back up by about 4:30 p.m. ET, a spokeswoman for the Lifespan system of hospitals told The Providence Journal.
In Lexington, Ky., Wednesday night, NBC station WLEX reported that visitations at the Fayette County Detention Center, normally from 6 to 10 p.m., were cancelled because systems were still down.
The National Science Foundation's computers at its Arlington, Va., headquarters were also down Wednesday.