The US continues to relay more spam than any other country, at 15.6 per cent of all junk mail, according to a new report from security firm Sophos.
Notorious countries like Russia are falling down the Sophos Dirty Dozen list, but the US remains in a strong first position, beating second-placed Brazil by a clear four percentage points.
The Sophos report also pointed to the growing use of social networking sites in malware attacks. URL shortening services are being used to fool users into thinking that a link is safe, when it actually sends them to a compromised web site.
The firm warned that, as the popularity of social networking sites continues to grow, so will the number of attacks designed to exploit them.
"Clearly the problem isn't going away, as is illustrated by the large number of sprawling spam campaigns we see on a daily basis," said senior Sophos technology consultant Graham Cluley.
"Although it may seem encouraging to see reductions in the volume of spam that certain countries are contributing, the authorities, internet service providers and home users across the world need to be doing more to crack down on the spam problem."
Although the US is the worst country for relaying spam, Asia is the worst continent, according to Sophos. Almost a third of all spam mails came from the area, and South Korea and China are the worst offenders. Europe was second with just over 21 per cent.
Cluley added in a blog post that people are mistaken if they believe that the threat of hack attacks comes from anywhere but their own compromised machines.
"Much attention is given by the powers that be to the threat of cyber terrorists and rogue states launching attacks, but the fact is that it could be your sister-in-law who is helping the spammers because her home PC is not properly defended," he said.