Clearswift, a provider of software for managing and securing electronic communications, announced in its "Spam Index" report for December that spam selling healthcare products, such as Viagra and diet pills, continues to constitute almost half of all email. The analysis also revealed a rise in finance- and product-related spam.

The dominance of healthcare-related spam in December's report marks the first time there has been a month-to-month trend in spam activity. "The fact that we are now seeing consistent trends suggests the spam market is maturing," Alyn Hockey, director of research at Clearswift, said.

Finance-related spam drew attention because it jumped from 13 to 22 percent in December. Likewise, product-related spam jumped from 10 to 19 percent. These numbers, according to Clearswift, suggest spammers targeted consumers with products such as radio-controlled cars and helicopters while offering cheap loans to give them a helping hand for the holiday season. Clearswift's figures, which were extracted from the thousands of unsolicited email messages received by Clearswift on a weekly basis, are made up of spam generated by seeding email accounts and spam submissions forwarded to Clearswift by its 20 million users.