Spam volumes decreased by 24% in the fourth quarter of 2009 sequentially, with an average of approximately 135.5 billion spam messages per day, according to McAfee’s threat report for the fourth quarter of 2009.

The report found that malware including fake security software, attacks on social networks, and auto-run USB infections, continued to rise significantly last year. The internet-based, web 2.0-centric attacks and threats on portable storage devices played a vital role in 2009, contributing to increase in threats. Cybercriminals used social networking sites to target a new generation of victims, with Koobface activity increasing considerably during the latter part of 2009.

According to the report, China topped the Zombie production with 12% in Q4 surpassing the US, which has dropped from 13.1% in Q3 to 9.5% in Q4 2009. Brazil ranked third followed by Russia and Germany. However, US still remains number country in spam production followed by Brazil and India, while Ukraine and Germany joined the list of top 10 countries producing spam for the first time in 2009.

North America reported highest malicious content, with EMEA in second followed by Asia/Pacific. In Europe, Germany holds the number one spot, followed by the Netherlands and Italy. China is the chief host for malicious content in Asia, followed by Russia and South Korea, with Brazil as the top hosting country in that region.

China was by far the number one country hosting SQL-injection attacks with 54.4%. The firm said that it also saw a number of client-targeted attack attempts to exploit Flash and Acrobat reader due to the growing popularity of Adobe applications.

The report also highlights the most significant spam-generating stories in 2009 as well as the rise of political hacktivism in countries like Poland, Latvia, Denmark and Switzerland. Spammers utilised headlines heavily in 2009, taking advantage of breaking news stories, global tragedies and timely events.

Mike Gallagher, senior vice president and chief technology officer of McAfee Labs, said: “In Q4, we saw spam activity drop, but identified some interesting trends developing in terms of the geographic distribution of cyber threats and the types of threats executed.

“China emerged as the worldwide leader in both zombie production and the execution of SQL-injection attacks, while internet-based attacks played a bigger role and will continue to do so as cybercriminals target the most popular social destinations in 2010.