The ‘Internet doomsday’ that threatened to knock thousands off the Internet passed with little incident. (TIM WIMBORNE/REUTERS)

Call it the doomsday that wasn’t.

Thousands worried that they would lose Internet access after the Federal Bureau of Investigation pulled the plug Monday on a safety net set up to keep machines infected with a widespread virus online.

But like the Y2K bug before it, the aftermath from the ‘Internet doomsday’ virus passed with little incident.

The virus, called DNS Changer, sent computers to false sites by interfering with how they direct traffic; the FBI’s backup servers temporarily set things right while giving uses time to clean up their machines. Once it took the servers down, the FBI said, any computer still infected with the virus would be cut off from the Web.

In addition to setting up the system, the FBI also set a massive awareness campaign in motion. Businesses were among the first to offer quick fixes for their computers. Technology companies such as Google, Facebook and Microsoft helped with the task of reaching out to individual Web users. Internet service providers such as Comcast reached out to their customers though e-mail, mail and in-browser notifications.

The education campaign appeared to work. Internet service providers such as Cox Communications and Comcast said that they had customer service representatives standing by to deal with a spike in calls that never came. Comcast spokesman Charlie Douglas said that the company had only fielded a “minuscule” amount of calls.

In the end, FBI spokeswoman Jenny Shearer said that, ultimately, switching off the servers was “not that big a deal.”

Barry Greene, a volunteer with an awareness organization called the DNS Changer Working Group, credited the public-private partnership for the uneventful day.

“When it comes to industry collaboration, this has been really good for us,” he said.

Worst-case scenarios indicated that 46,000 U.S. Internet users could lose access. And Greene said that that many machines are probably cut off from the Web today, but it’s not clear how many of those are computers that people actively use.

“We suspect that there are some computers that don’t have anyone driving them — that’s a hypothesis we have,” Greene said. Douglas said that the affected machines could be the second or third devices in users’ homes, which people may not have bothered to check.

Greene said that part of what worked for the awareness campaign around DNS Changer was that it was easy for average users to use and kept the anxiety level down. Web sites showed users a simple green or red indicator to show whether they were infected, and pointed to easy tools to get rid of the threat if necessary.

The working group will continue to monitor the backup servers for another 24 hours to find out more about the computers still affected. “Some of the data we collect can help us the next time.”

And there will be a next time, experts say. Malware attacks increase every year and have a greater potential for real harm. With developing technologies connecting more areas of life to the Internet, a widespread attack could have unintended consequences for things such as video conferencing, health-care systems or utilities infrastructure.

“We rely so much on the Internet and computers in general, it leads us to be susceptible to attacks,” said Kenneth Wisnefski, an Internet security expert and chief executive of the online security firm WebiMax.

Education is key, Wisnefski said. He recommended that Internet service providers release short videos for their customers to teach them how to identify potential problems and deal with widespread viruses.

“People trust the Internet so much,” he said. “When things like this start to happen it’s definitely a concern.”

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