During the second quarter of 2009, the U.S. continued to relay more spam than any other country, accounting for 15.6 percent of global spam traffic, according to security firm Sophos.

Brazil trailed the U.S. accounting for 11.1 percent of global spam traffic followed by Turkey at 5.2 percent and India with 5 percent.

“If America could clean up its compromised PCs it would be a considerable benefit to everyone around the world who uses the net,” said Graham Cluley, senior technology consultant for Sophos.

“All web users need to properly defend their computers from attack, and pledge to never act upon spam messages.”

Sophos also found URL shortening services are being used to trick users to click on links that send them to malicious sites. The firm warned as social networking continues to grow in popularity that poorly protected computer users could be more vulnerable to a wider range of spam attacks.

“Clearly the problem isn’t going away, as is illustrated by the large number of sprawling spam campaigns we see on a daily basis,” continued Cluley.

“Although it may seem encouraging to see reductions in the volume of spam that certain countries are contributing, authorities, ISPs and home users across the world need to be doing more to crack down on the spam problem.”

Overall by continent, Asia continues to be the biggest offender. Almost a third of spam messages originated in the region for the second quarter of 2009, with the nations of South Korea and China being the biggest contributors.