Users have probably noticed a  drop in spam volumes over the last couple of days. That's because the web host responsible for generating about 75% of the world's spam was shut down in the US on Tuesday. Although spammers are quickly finding new servers, spam volumes have been much lower than usual for most of the week.

McColo, the web host in the US, was shut down by its ISPs (Internet service providers) after the Washington Post unveiled it as the world's largest spam server after a four-month investigation.
The web host included customers involved in remotely managing botnets to those selling fake pharmaceuticals and security products or e-mail pornography.
It hasn't been determined if McColo can be held responsible for its customers acitivities, though, and there has been no action taken by authorities.
The host is based in California.