The Federal Trade Commission’s unprecedented recent takedown against troubled Web hosting provider 3FN.net has had an immediate — if little noticed — impact on the level of spam sent worldwide, and the number of infected PCs doing the spamming, according to multiple sources. Experts say the drop in spam probably is not visible to most Internet users or even operators of large networks, as the decrease is within the upper ranges of daily fluctuations in spam volumes. Still, the preliminary results indicate that a large number of spam-spewing zombie PCs were being coordinated out of severs hosted at 3FN. According to botnet expert Joe Stewart, director of malware research at Atlanta based SecureWorks, 3FN was home to a large number of command-and-control servers for the Cutwail spam botnet, one of the world’s largest. As of last week, Stewart said he was tracking upwards of 400,000 spam zombies infected with Cutwail