A new botnet called Festi' is fast becoming one of the main spambots on the net, putting out 1.5 to three billion spam mails per day globally.
Symantec's MessageLabs Intelligence has been tracking the botnet since August, and said it now accounted for three to six per cent of global spam daily.
Festi's growth was due to an increase in the amount of spam sent from each Festi bot as well as the recruitment of new bots to the cause.
The first variant of spam it is spewing out are mails selling male enhancement pills leading to a Canadian pharmacy website. The second is aimed at selling watches and contains links to .com domains.
Symantec security researcher Daren Lewis said in a blog post: "In terms of Festi's global ranking among the botnets, Festi has become one of the spamming heavyweights."
"Currently, Festi is fifth after the giant big four' botnets: Cutwail, Bagle, Grum and Rustock (which among them account for more than 80 per cent of global spam)," he added.
