Nine out of the 19 full solutions tested saw the percentage of spam they missed at least double, with only three products improving their catch rates. A spam email was almost twice as likely to make it to a user's inbox compared to the previoustest.
Most products had more difficulty with legitimate emails as well, with only four solutions correctly identifying all of them, and products had even more difficulty blocking phishing emails. More than half of the solutions missed at least 10% of the emails in a dedicated feed of phishing emails.
"Spam has been a relatively good news story in recent years, with spam levels declining while catch rates remained high," said VB's Anti-Spam Test Director, Martijn Grooten. "But in spam filtering, the devil is in the details, and when we look at these details, we see more emails slipping through the maze."
This is not the first time Virus Bulletin has observed a drop in products' spam catch rates: a similar drop was observed early last year, with the decline continuing throughout the first half of the year.
Grooten continued: "It is obvious why missing a phishing email is bad and could have serious consequences, but even an ordinary spam email can be much more than a nuisance in the inbox. A lot of today's spam has malware attached or links to exploit kits and it just takes one click on a link in an email that shouldn't have been there to grant cyber crooks access to your PC or mobile device. We will be keeping a close eye on spam catch rates, and hoping that the filters manage to catch up more quickly this year."