Porn spam increases by 350 percent

The company's June index revealed pornographic e-mails comprised only 4.8 percent of all spam for the month. However, pornographic e-mails made up 17.2 percent of all spam in July.

"Spammers are working overtime. In what appears to be an attempt to match supply with demand, healthcare spam (most of which was Viagra) has also increased. This upsurge is similar to the same period last year -- spammers increase their pornographic output during the summer months," said Peter Croft, managing director, Clearswift Asia Pacific.

Croft said a big risk is damage to corporate reputations when the e-mails are circulated. He added that most of these types of e-mails are also designed to dupe users into opening viruses hidden in Web links or zipped attachments.

In an attempt to salvage its reputation, Viagra manufacturer, Pfizer, has recently begun a legal campaign against spammers peddling potentially counterfeit pills via e-mail and Web sites. Recent research conducted by Pfizer revealed 25 percent of men believed the pharmaceutical giant itself was responsible for sending Viagra-themed spam.

Based on the success of the monthly spam index, Clearswift has also launched a virus index. The first findings support predictions of IT security experts' views that malicious activity is becoming progressively potent, with zombie and peer-to-peer networks facilitating the spread.

Zafi-B, written by this year's most prolific malware writer Sven Jaschan, tops the virus index followed by Netsky-P and Netsky-D.