Studies done two weeks ago by OpenDNS and group had suggested that as many as 4 percent of PCs might have been hit with the Conficker worm, but the Working Group's analysis suggests the number is likely much lower.

"We're hoping that publishing these numbers will throw a little bit of reality into the equation," said Andre DiMino, cofounder of The Shadowserver Foundation and a member of the Working Group. He does not believe that 4 percent of PCs were infected. "It's hard to make a case for that right now," he said.