According to Brian Krebs of Krebs on Security, researchers with the University of California, San Diego, have collated their first batch of data on spam purchases in the US.
And, he says, it appears that the bulk of purchases continue to be for male enhancement drugs such as Viagra and Cialis, items which Chris Kanich, a researcher with the UCSD told Krebs, are too embarrassing for people to talk to their doctors about.
Interestingly, some drugs are also cheaper to order through spam outlets, said Kanich, who is also the lead researcher on the project.
"Previous estimates of monthly revenue from spam have varied dramatically, from $300,000 to more than $58 million. The UCSD researchers found that the largest rogue internet pharmacies generate between $1 million and $2.5 million in sales each month, although they caution that their estimates are conservative", says Krebs in his latest security blog.
"Kanich says the figures show that although the spam-advertised market is substantial, it is not nearly as big as some have claimed, and falls short of annual expenditures on technical anti-spam solutions by corporations and ISPs", he adds.
Krebs goes on to say that the researchers arrived at their dollar estimates by mining transaction data from seven of the top spam-advertised pharmacies.
By making targeted "buys" from each pharmacy brand, they discovered that each of the pharmacy assigns sequential order numbers to individual purchases.
"Thus, from any pair of purchases, the UCSD team could determine the total transaction volume for the interval between their two purchases by subtracting the first order number from the second", he noted.