Although the U.S. still remains the worst spam relaying offender, according to the latest "Dirty Dozen" national spam offenders report conducted by security firm Sophos, it now accounts for only 26.35 per cent of unsolicited emails, compared to 41.50 per cent in the same period last year.
The study found that the U.S. and Canada have done well to reduce their contribution to the problem. The sharp drop in spam sent from North American computers was attributed to a number of factors, including jail sentences for spammers, tighter legislation and better system security.
"Efforts such as ISPs sharing knowledge on how to crack down on spammers, and authorities enforcing the CAN-SPAM legislation, have helped North America tackle the spammers based on their doorsteps. Some of the most prolific spammers have been forced to either quit the business or relocate overseas as a result," said Graham Cluley, senior technology consultant for Sophos.
"The introduction of Windows XP SP2 a year ago, with its improved security, has also helped better defend home users from computer hijacking. The worry now is that devious spammers will turn to other net-based money-making schemes, such as spyware and identity theft malware to make their dirty money."
Feeling the impact of international awareness and country-specific legislation, spammers are increasingly turning to illegitimate providers to fuel their success and their key partners in crime are virus writers and hackers. Sophos' study estimates that 60 per cent of spam originates from zombie PC infected with malware.
By taking control of unprotected PCs, hackers can relay spam, launch denial-of-service attacks or steal user information, without the computer owners being any-the-wiser, the study research noted.
"There are fortunes to be made from the dark side of the internet, and spammers who are finding it harder to sell goods via bulk email are likely to turn to other criminal activities," added Cluley.
"What the chart reveals is that spammers and virus writers can exploit unprotected computers anywhere in the world to send out their unwanted messages - everyone has a part to play in the fight against spam."
The top 12 spam relaying countries are as follows, with the figures in brackets denoting the spam relayed by each country in the same period in 2004:
April - September, 2005
1. United States 26.35% (41.50%)
2. S Korea 19.73% (11.63%)
3. China (inc Hong Kong) 15.70% (8.90%)
4. France 3.46% (1.27%)
5. Brazil 2.67% (3.91%)
6. Canada 2.53% (7.06%)
7. Taiwan 2.22% (0.86%)
8. Spain 2.21% (1.04%)
9. Japan 2.02% (2.66%)
10. United Kingdom 1.55% (1.07%)
11. Pakistan 1.42% New Entry
12. Germany 1.26% (1.02%)
Others: 18.88% (18.10%)