The Anti-Spam Technical Alliance, which includes America Online Inc., Yahoo Inc., Microsoft Corp. and EarthLink Inc., urged all Internet providers to police their networks more aggressively and cut off machines suspected of being launching pads for spam.

By some estimates, hundreds of thousands of computers around the world have been infected with software that lets them be used without their owners’ knowledge. Such machines now account for as much as 40 percent of all spam.

Read more at Yahoo News.