"This time it's different. It's using drive-by downloads," Huang said. "You visit a site and then you see a fake antivirus pop up." It looks like a genuine antivirus message, he said, and is already installed on the victim's computer. ""Even if you reboot, it's already there."

If the cybercriminals were able to get their bad ads on Google's and Microsoft's networks, they'll probably try to do the same thing on other networks too, he said.

Amorize planned to publish on Friday evening.

The IDG News Service