“Graham Cluley, senior technology consultant at Sophos, thinks there are several reasons for the recent decline of Rustock’s, the botnet responsible for a large amount of global spamming, activity.

“One of the biggest reasons Rustock’s spamming activity has declined is that the affiliate programme, Spamit, which supplies lots of the content for the pharmaceutical spam emails it sends, has shut down. So in effect, Rustock needs to find a new large client to send spam on behalf of.

The other trend in this area which analysts have noted is that spammers have started to attack social networks, such as Facebook, much more, rather than email services.”