Now, said Grasso, "the full court press is on to get people to address this problem." And it's up to computer users to check their PCs.
This is what happened:
Hackers infected a network of probably more than 570,000 computers worldwide. They took advantage of vulnerabilities in the Microsoft Windows operating system to install malicious software on the victim computers. This turned off antivirus updates and changed the way the computers reconcile website addresses behind the scenes on the Internet's domain name system.
The DNS system is a network of servers that translates a web address — such as www.ap.org — into the numerical addresses that computers use. Victim computers were reprogrammed to use rogue DNS servers owned by the attackers. This allowed the attackers to redirect computers to fraudulent versions of any website.
The hackers earned profits from advertisements that appeared on websites that victims were tricked into visiting. The scam netted the hackers at least $14 million, according to the FBI. It also made thousands of computers reliant on the rogue servers for their Internet browsing.
When the FBI and others arrested six Estonians last November, the agency replaced the rogue servers with Vixie's clean ones. Installing and running the two substitute servers for eight months is costing the federal government about $87,000.
The number of victims is hard to pinpoint, but the FBI believes that on the day of the arrests, at least 568,000 unique Internet addresses were using the rogue servers. Five months later, FBI estimates that the number is down to at least 360,000. The U.S. has the most, about 85,000, federal authorities said. Other countries with more than 20,000 each include Italy, India, England and Germany. Smaller numbers are online in Spain, France, Canada, China and Mexico.
Vixie said most of the victims are probably individual home users, rather than corporations that have technology staffs who routinely check the computers.