The Storm worm is still building a mega-botnet and distributing a significant amount of spam. The worm, which was identified in January 2007, is a classic scam that emails individuals with the suggestion that they invest in certain so-called penny stocks. Once the investment is made and share prices increase, the scammers dump their shares and leave victims with essentially worthless stock.

The worm has adopted many forms since its discovery and is now being propagated by MP3 files bearing as many as 40 different titles, such as beatles.mp3 and elvis.mp3. In the files, a computer-generated voice tells the recipient to purchase a certain penny stock. The playback speed of the file has been manipulated, making it difficult to identify concretely.

SecureWorks, a computer security firm, also pointed out this week that the Storm botnet is sub-dividing, suggesting that parts of the malicious network may be up for sale.