Internet Blackout on the Way for Many

Hundreds of thousands of Internet users whose computers are infected with a particularly nasty virus are now unable to access the Web.

The Federal Bureau of Investigation shut down Internet servers that it temporarily set up to support those affected by malicious software, called DNSChanger. Turning off those servers knocked all those still infected offline.

Over the past five years, a group of six Estonian cybercriminals infected about 4 million computers around the world with DNSChanger. The malware redirected infected users' Web searches to spoofed sites with malicious advertisements.

In November 2011, the FBI and some overseas partners arrested those responsible, commandeered their servers, and attempted to warn those affected to get rid of the virus.

The FBI did not immediately take down the rogue servers, as infected computers would have lost Internet access, an FBI spokesman said.

To remedy the problem, the FBI had the nonprofit Internet Systems Consortium set up temporary servers. That way, computer owners would have time to get rid of their malware.

The servers were supposed to be shut down in March, but hundreds of thousands remained infected. Nearly 211,000 computers worldwide (about 42,000 in the United States) still have the virus, according to the FBI's latest count on Monday. That's a large number, but it's a very small subset of the 1.6 billion PCs worldwide, of which an estimated 339 million are in the United States.

Still, the FBI decided to give people even more time to check for the malware, extending the deadline until July. The agency now says the time has come to cut the cord, and the emergency servers were shut down Monday morning.

Though the FBI tried to send notifications to those infected, it could not identify all of them, a spokesman said.