Anti-spam tools are catching fewer messages in the wild, according to tests from Virus Bulletin.
The security testing firm said that its latest round of VBSpam anti-spam tests found that, on average, security tools were catching fewer spam messages and many were showing a higher rate of false positive detections.
The tests found that of of 19 products tested, nine delivered over twice as many failed detections as previous tests. Additionally, researchers said that just three of the products they tested showed any improvement.
Among the highest-performing products were Libra Esva, Spam Titan and BitDefender. Anti-spam tools from NetMail, Fortimail and ESET also performed well in the tests.
Despite the lower rates, anti-spam products performed relatively well in the tests with the lowest-rated filters managing to catch more than 98 percent of spam messages with a false positive rate of less than 0.25 percent.
Still, researchers believe that the declining ability to catch spam messages could put users at risk for attack, particularly as malware writers increasingly look to bundle multiple attack methods and infection techniques into their operations.
"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," said Virus Bulletin anti-spam test director Martijn Grooten.
"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."