The all so hated billions of spam messages are coming from a surprisingly small number of zombie networks, also known as botnets, according to net security firm Marshall, who analyzed the numbers. There is a big variation from each and every one of the group, but the metrics for the passed month indicate that 85 percent of the spam was generated by the infamous six.

The king of unwanted messages in February was the Srizbi botnet, which accounted for 39 percent of the total, and the runner-up was the Rustock botnet, responsible for 21 percent of the spam. If there was a contest for the zombie machine networks, the former would win by a landslide. Third in the list was the Mega-D botnet, who encountered a big problem in mid-February control-wise, and it was only 10 days later that it managed to pump out junk mail, infecting personal computers with the Ozdok Trojan. Even so, the network is to be held accountable for 11 percent of the spam caught by Marshal filters.

The fourth and fifth positions were held by the Hacktool.Spammer and botnets associated with the Pushdo family of malware, according to the security firm. The last surprise was actually the world renowned Storm botnet, which allegedly has the biggest and most dangerous zombie networks at its disposal. Only three percent of the total unwanted messages originated from its team and hosts.

"The size of a botnet, measured by how many bots it has, does not necessarily correlate with how much spam it sends. Our team has observed huge variations in the rate at which different spambots pump out spam," said Bradley Anstis, VP of products at Marshal.

Additional findings from Network Box, the United States have managed to create and send the most spam and spread the most viruses, with numbers being 15 percent, respectively 13 percent.