An American ISP was knocked offline earlier this week after several internet security companies alleged that it was helping spammers send out junk mail including online fraud and child pornography.
McColo has apparently been being watched for several years by researchers who believed it was hosting phishing and spamming activities.
And when it was taken offline, experts claimed that spam rates declined by as much as 40-75% immediately.
This, as IT Pro Portal puts it, suggests a "substantive portion of world’s spam was hosted by McColo".
Jart Armin, who has been investigating McColo, said in a report that the ISP was hosting command and control systems for a large number of botnets, including Dedler, Mega-D, Pushdo, Srizbi, and Rustock.
Terrifyingly, each of these botnets has control of around an average of 600,000 slaved computers.
The report further states, "Research and contribution has shown at least 40 confirmed CP websites, name servers, and CP payment systems recently served by McColo".