According to Help Net Security, SpamThru Trojan is responsible for a vast increase in both spam and virus infection among PC users:

"The developers of SpamThru exploited numerous tactics to eliminate detection and enhance outreach such as releasing new strains of the Trojan at regular intervals in order to confuse traditional anti-virus signatures detection. Furthermore, SpamThru employed the "spam cannon" technique and by utilizing a template for each spam it sent out and combining it with a list of email addresses, each zombie was able to pump out millions of spam emails and avoid detection."

Pretty much the same tactic was used by Warezov, another Trojan that has plagued the web over the last month.

Still, I was really shocked to read that almost 73% of all e-mails were in fact spam, which might be also carrying a virus that has a potential to turn your computer into a zombie.

Once again, keep your anti-virus software updated, your OSs patched and make it default for your e-mail reader to block displaying remote images and Javascript. And never ever click on any links you get in unsolicited e-mail, not even if it swears to its mother's grave to make you loose weight or stop smoking with magical pills.