MessageLabs claims that we have seen a drop in spam by more than a third, thanks to action by Microsoft against one of the biggest botnets that serve it up. According to MessageLabs in 2010, 88 percent of all spam emails were sent by botnets, and of that botnet-originated spam, Rustock was responsible for an average of 28 percent.

Microsoft's action in taking out Rustock has unsurprisingly had a substantial impact on spam levels. But MessageLabs reports that other botnets have increased spam production over the same period, making it likely that previous spam volumes will be resumed soon enough.

However the data does give some positive news. It appears that ten botnets were responsible for about 74 percent of all spam. While hitting these botnets would be tricky, it is not impossible and spam could be reduced to reasonable levels. Botnets are also taking a hit as the ancient Windows XP is being replaced and infected systems are being fixed.

Microsoft's action might also mean that the law has to be changed. Vole had to use trademark law to have the server hardware seized. Existing anti-spam legislation only allows domain names to be taken which would not have switched off Rustock.