Microsoft report finds large drop in spam emails

There has been a sharp drop in the number of spam emails detected and blocked by Microsoft. (Microsoft image)

The number of spam emails blocked before reaching inboxes has dropped by two-thirds, according to Microsoft’s Security Intelligence Report.

The report (PDF, 168 pages), released today, finds that around 21.9 billion spam emails were blocked in May 2011 using Microsoft Online Protection for Exchange, down from 89.2 billion messages in July 2010.

The report credits the takedown of the Cutwail and Rustock botnets as having “a positive effect on improving the health of the email ecosystem.” In late September, Microsoft announced the Kelihos botnet was dismantled.

What’s the most popular type of blocked spam? That would be a category called “Pharmacy–Non-sexual” with 28 percent of emails. The next most prevalent forms of spam were non-pharmacy product ads, 419 (Nigerian) scams and financial services. Combined, these categories accounted for two-thirds of blocked emails.